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  • 1. Babkevich, P.
    et al.
    Jeong, M.
    Matsumoto, Y.
    Kovacevic, I.
    Finco, A.
    Toft-Petersen, R.
    Ritter, C.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. Ecole Polytech Fed Lausanne, ICMP, Lab Quantum Magnetism, Switzerland.
    Nakatsuji, S.
    Ronnow, H. M.
    Dimensional Reduction in Quantum Dipolar Antiferromagnets2016In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 116, no 19, article id 197202Article in journal (Refereed)
    Abstract [en]

    We report ac susceptibility, specific heat, and neutron scattering measurements on a dipolar-coupled antiferromagnet LiYbF4. For the thermal transition, the order-parameter critical exponent is found to be 0.20(1) and the specific-heat critical exponent -0.25(1). The exponents agree with the 2D XY/h(4) universality class despite the lack of apparent two-dimensionality in the structure. The order-parameter exponent for the quantum phase transitions is found to be 0.35(1) corresponding to (2 + 1)D. These results are in line with those found for LiErF4 which has the same crystal structure, but largely different T-N, crystal field environment and hyperfine interactions. Our results therefore experimentally establish that the dimensional reduction is universal to quantum dipolar antiferromagnets on a distorted diamond lattice.

  • 2.
    Benedek, Peter
    et al.
    Swiss Fed Inst Technol, Dept Informat Technol & Elect Engn, CH-8092 Zurich, Switzerland..
    Yazdani, Nuri
    Swiss Fed Inst Technol, Dept Informat Technol & Elect Engn, CH-8092 Zurich, Switzerland..
    Chen, Hungru
    Univ Bath, Dept Chem, Bath BA2 7AY, Avon, England..
    Wenzler, Nils
    Swiss Fed Inst Technol, Dept Informat Technol & Elect Engn, CH-8092 Zurich, Switzerland..
    Juranyi, Fanni
    Paul Scherrer Inst, Lab Neutron Scattering & Imaging, CH-5232 Villigen, Switzerland..
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Islam, M. Saiful
    Univ Bath, Dept Chem, Bath BA2 7AY, Avon, England..
    Wood, Vanessa C.
    Swiss Fed Inst Technol, Dept Informat Technol & Elect Engn, CH-8092 Zurich, Switzerland..
    Surface phonons of lithium ion battery active materials2019In: SUSTAINABLE ENERGY & FUELS, ISSN 2398-4902, Vol. 3, no 2, p. 508-513Article in journal (Refereed)
    Abstract [en]

    Surfaces of active materials are understood to play an important role in the performance and lifetime of lithium-ion batteries, but they remain poorly characterized and therefore cannot yet be systematically designed. Here, we combine inelastic neutron scattering and ab initio simulations to demonstrate that the structure of the surface of active materials differs from the interior of the particle. We use LiFePO4 (LFP) as a model system, and we find that carbon coating influences the Li-O bonding on the (010) LFP surface relative to the bulk. Our results highlight how coatings can be used to systematically engineer the vibrations of atoms at the surface of battery active materials, and thereby impact lithium ion transport, charge transfer, and surface reactivity.

  • 3.
    Brena, Barbara
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Palmgren, Pål
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Nilson, Katharina
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Hennies, F.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Agnarsson, Björn
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Önsten, Anneli
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    InSb-TiOPc interfaces: Band alignment, ordering and structure dependent HOMO splitting2009In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 603, no 20, p. 3160-3169Article in journal (Refereed)
    Abstract [en]

    Thin films of titanyl phthalocyanine (TiOPc) have been adsorbed on InSb(1 1 1) (3 x 3) and InSb(1 0 0) c(8 x 2) surfaces and studied with respect to their electronic structure using photoemission (PES), density functional theory (DFT) and scanning tunneling microscopy (STM). The interface chemical interaction is weak in both cases; no adsorbate induced surface band bending is observed and the energy level alignment across the interface is determined by the original position of the substrate Fermi level and the charge neutrality level of the molecule. Room temperature adsorption results in disordered films on both surfaces. The behaviors after annealing are different; on InSb(1 0 0) well-ordered molecular chains form along and on top of the In-rows, whereas on (1 1 1) no long range order is observed. The disorder leads to intermolecular interactions between the titanyl group and neighboring benzene rings leading to a split of TiOPc HOMO (highest occupied molecular orbital) by as much as 0.8 eV.

  • 4. Chang, J.
    et al.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Pailhes, S.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Lipscombe, O. J.
    Hayden, S. M.
    Patthey, L.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Mesot, J.
    Anisotropic breakdown of Fermi liquid quasiparticle excitations in overdoped La2-xSrxCuO42013In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 4, p. 2559-Article in journal (Refereed)
    Abstract [en]

    High-temperature superconductivity emerges from an un-conventional metallic state. This has stimulated strong efforts to understand exactly how Fermi liquids breakdown and evolve into an un-conventional metal. A fundamental question is how Fermi liquid quasiparticle excitations break down in momentum space. Here we show, using angle-resolved photoemission spectroscopy, that the Fermi liquid quasiparticle excitations of the overdoped superconducting cuprate La1.77Sr0.23CuO4 is highly anisotropic in momentum space. The quasiparticle scattering and residue behave differently along the Fermi surface and hence the Kadowaki-Wood's relation is not obeyed. This kind of Fermi liquid breakdown may apply to a wide range of strongly correlated metal systems where spin fluctuations are present.

  • 5.
    Chang, Johan
    et al.
    Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, Villigen.
    Pailhés, Stephane
    Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, Villigen.
    Shi, Ming
    Swiss Light Source, Paul Scherrer Institute, Villigen.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Voigt, Jörg
    Institute for Solid State Research, Forschungszentrum Jülich.
    Perez, V.
    Swiss Light Source, Paul Scherrer Institute, Villigen.
    Patthey, Luc
    Swiss Light Source, Paul Scherrer Institute, Villigen.
    Momono, Naoki
    Department of Physics, Hokkaido University, Sapporo.
    Oda, Migaku
    Department of Physics, Hokkaido University, Sapporo.
    Ido, Masayuki
    Department of Physics, Hokkaido University, Sapporo.
    Schnyder, A.
    Condensed Matter Theory Group, Villigen.
    Mudry, C.
    Condensed Matter Theory Group, Villigen.
    Mesot, Joël
    Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, Villigen.
    When low- and high-energy electronic responses meet in cuprate superconductors2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 22, p. 224508-Article in journal (Refereed)
    Abstract [en]

    The existence of coherent quasiparticles near the Fermi energy in the low-temperature state of high-temperature superconductors has been well established by angle-resolved photoemission spectroscopy (ARPES). We present a study of La1.83Sr0.17CuO4 in the superconducting state and report an abrupt change in the quasiparticle spectral function, as we follow the dispersion of the ARPES signal from the Fermi energy to 0.6 eV. The interruption in the quasiparticle dispersion separates coherent quasiparticle peaks at low energies from broad incoherent excitations at high energies. We find that the boundary between these low-energy and high-energy features exhibits a cosine-shaped momentum dependence, reminiscent of the superconducting d-wave gap. Further intriguing similarities between characteristics of the incoherent excitations and quasiparticle properties suggest a close relation between the electronic response at high and low energies in cuprate superconductors.

  • 6.
    Chang, Johan
    et al.
    Laboratory for Neutron Scattering, ETH Zurich, Paul Scherrer Institute, Villigen.
    Shi, Ming
    Swiss Light Source, Paul Scherrer Institute, Villigen.
    Pailhés, Stephane
    Laboratory for Neutron Scattering, ETH Zurich, Paul Scherrer Institute, Villigen.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Bendounan, Azzedin
    Laboratory for Neutron Scattering, ETH Zurich, Paul Scherrer Institute, Villigen.
    Sassa, Yasmine
    Laboratory for Neutron Scattering, ETH Zurich, Paul Scherrer Institute, Villigen.
    Patthey, Luc
    Swiss Light Source, Paul Scherrer Institute, Villigen.
    Momono, Naoki
    Department of Physics, Hokkaido University, Sapporo.
    Oda, Migaku
    Department of Physics, Hokkaido University, Sapporo.
    Ido, Masayuki
    Department of Physics, Hokkaido University, Sapporo.
    Guerrero, S.
    Condensed Matter Theory Group, Paul Scherrer Institute, Villigen.
    Mudry, C.
    Condensed Matter Theory Group, Paul Scherrer Institute, Villigen.
    Mesot, Joël
    Laboratory for Neutron Scattering, ETH Zurich, Paul Scherrer Institute, Villigen.
    Anisotropic quasiparticle scattering rates in slightly underdoped to optimally doped high-temperature La2-xSrxCuO4 superconductors2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 20, p. 205103-Article in journal (Refereed)
    Abstract [en]

    An angle-resolved photoemission study of the scattering rate in the superconducting phase of the high-temperature superconductor La2-xSrxCuO4 with x=0.145 and x=0.17, as a function of binding energy and momentum, is presented. We observe that the scattering rate scales linearly with binding energy up to the high-energy scale E-1 similar to 0.4 eV. The scattering rate is found to be strongly anisotropic, with a minimum along the (0,0)-(pi,pi) direction. A possible connection to a quantum-critical point is discussed.

  • 7.
    Claesson, Thomas
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Månsson, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Dallera, Claudia
    INFM-Dipartimento di Fisica, Politecnico di Milano, Italy.
    Venturini, Federica
    Europ. Synchrt. Radiation Facility, Grenoble, France.
    De Nadaï, Celine
    Europ. Synchrt. Radiation Facility, Grenoble, France.
    Brookes, Nicholas B.
    Europ. Synchrt. Radiation Facility, Grenoble, France.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Angle Resolved Photoemission from Nd(1.85)Ce(0.15)CuO(4) using High Energy Photons: A Fermi Surface Investigation2004In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 93, no 13, p. 136402-1-136402-4Article in journal (Refereed)
    Abstract [en]

    We have performed an angle resolved photoemission study on a single crystal of the optimally electron doped (n-type) cuprate superconductor Nd2-xCexCuO4 (x=0.15) at a photon energy of 400 eV. The Fermi surface is mapped out and is, in agreement with earlier measurements, of hole-type with the expected Luttinger volume. However, comparing with previous low energy measurements, we observe a different Fermi surface shape and a different distribution of spectral intensity around the Fermi surface contour. The observed Fermi surface shape indicates a stronger electron correlation in the bulk as compared to the surface.

  • 8.
    Claesson, Thomas
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Finazzi, M.
    Dallera, C.
    Cezar, J. C.
    Brookes, N. B.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Transfer of spectral weight across the magnetic transition in CoO: novel results from high-energy angle-resolved photoelectron spectroscopyManuscript (preprint) (Other academic)
  • 9.
    Claesson, Thomas
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Önsten, Anneli
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Shi, Ming
    Swiss Light Source, Paul Scherrer Institut, Switzerland.
    Sassa, Yasmine
    Laboratory for Neutron Scattering, Zürich, Paul Scherrer Institut.
    Pailhés, Stephane
    Laboratory for Neutron Scattering, Zürich, Paul Scherrer Institut.
    Chang, Johan
    Laboratory for Neutron Scattering, Zürich, Paul Scherrer Institut.
    Bendounan, Azzedin
    Synchrotron SOLEIL, L'Orme des Merisiers, France.
    Patthey, Luc
    Swiss Light Source, Paul Scherrer Institut, Switzerland.
    Mesot, Joël
    Paul Scherrer Institute, ETH Zürich, Switzerland.
    Muro, Takayuki
    Japan Synchrotron Radiation Research Institute.
    Matsushita, Tomohiro
    Japan Synchrotron Radiation Research Institute.
    Kinoshita, Toyohiko
    Japan Synchrotron Radiation Research Institute.
    Nakamura, Tetsuya
    Japan Synchrotron Radiation Research Institute.
    Momono, Naoki
    Department of Physics, Hokkaido University, Japan.
    Oda, Migaku
    Department of Physics, Hokkaido University, Japan.
    Ido, Masayuki
    Department of Physics, Hokkaido University, Japan.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    The electronic structure of La(1.48)Nd(0.4)Sr(0.12)CuO(4) probed by high- and low-energy angle-resolved photoelectron spectroscopy: Evolution with probing depth2009In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 80, no 9, p. 094503-1-094503-6Article in journal (Refereed)
    Abstract [en]

    We present angle-resolved photoelectron spectroscopy data probing the electronic structure of the Nd-substituted high-T-c cuprate La1.48Nd0.4Sr0.12CuO4. Data have been acquired at low and high photon energies, h nu=55 and 500 eV, respectively. The two extracted Fermi surfaces show significant differences. The differences can be attributed to either the change in probing depth suggesting dissimilarity of the intrinsic electronic structure between surface and bulk regions, or a considerable c-axis dispersion signaling a strong interlayer coupling. At both photon energies, considerable spectral weight is observed at all points along the Fermi surface and the intensity distribution as well as Fermi-surface shape observed at low as well as high photon energy is markedly different from what has been previously reported for La1.28Nd0.6Sr0.12CuO4 by Zhou [Science 286, 268 (1999)]. Document Type: Article

  • 10. Fatuzzo, C. G.
    et al.
    Sassa, Y.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Pailhes, S.
    Lipscombe, O. J.
    Hayden, S. M.
    Patthey, L.
    Shi, M.
    Grioni, M.
    Rønnow, H. M.
    Mesot, J.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Chang, J.
    Nodal Landau Fermi-liquid quasiparticles in overdoped La1.77Sr0.23CuO42014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 20, p. 205104-Article in journal (Refereed)
    Abstract [en]

    Nodal angle-resolved photoemission spectra taken on overdoped La1.77Sr0.23CuO4 are presented and analyzed. It is proven that the low-energy excitations are true Landau Fermi-liquid quasiparticles. We show that momentum and energy distribution curves can be analyzed self-consistently without quantitative knowledge of the bare band dispersion. Finally, by imposing Kramers-Kronig consistency on the self-energy Sigma, insight into the quasiparticle residue is gained. We conclude by comparing our results to quasiparticle properties extracted from thermodynamic, magnetoresistance, and high-field quantum oscillation experiments on overdoped Tl2Ba2CuO6+delta.

  • 11.
    Faure, Quentin
    et al.
    Univ Grenoble Alpes, CEA, INAC MEM, Grenoble, France.;Univ Grenoble Alpes, Inst NEEL, Grenoble, France..
    Takayoshi, Shintaro
    Univ Geneva, Dept Quantum Matter Phys, Geneva, Switzerland..
    Petit, Sylvain
    Univ Paris Saclay, CNRS, CEA, CE Saclay,Lab Leon Brillouin, Gif Sur Yvette, France..
    Simonet, Virginie
    Univ Grenoble Alpes, Inst NEEL, Grenoble, France..
    Raymond, Stephane
    Univ Grenoble Alpes, CEA, INAC MEM, Grenoble, France..
    Regnault, Louis-Pierre
    Univ Grenoble Alpes, CEA, INAC MEM, Grenoble, France..
    Boehm, Martin
    Inst Laue Langevin, Grenoble, France..
    White, Jonathan S.
    Paul Scherrer Inst, Lab Neutron Scattering & Imaging, Villigen, Switzerland..
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF. Paul Scherrer Inst, Lab Neutron Scattering & Imaging, Villigen, Switzerland.
    Rueegg, Christian
    Univ Geneva, Dept Quantum Matter Phys, Geneva, Switzerland.;Paul Scherrer Inst, Lab Neutron Scattering & Imaging, Villigen, Switzerland..
    Lejay, Pascal
    Univ Grenoble Alpes, Inst NEEL, Grenoble, France..
    Canals, Benjamin
    Univ Grenoble Alpes, Inst NEEL, Grenoble, France..
    Lorenz, Thomas
    Univ Cologne, Phys Inst 2, Cologne, Germany..
    Furuya, Shunsuke C.
    RIKEN, Condensed Matter Theory Lab, Wako, Saitama, Japan..
    Giamarchi, Thierry
    Univ Geneva, Dept Quantum Matter Phys, Geneva, Switzerland..
    Grenier, Beatrice
    Univ Grenoble Alpes, CEA, INAC MEM, Grenoble, France..
    Topological quantum phase transition in the Ising-like antiferromagnetic spin chain BaCo2V2O82018In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 14, no 7, p. 716-722Article in journal (Refereed)
    Abstract [en]

    Since the seminal ideas of Berezinskii, Kosterlitz and Thouless, topological excitations have been at the heart of our understanding of a whole novel class of phase transitions. In most cases, those transitions are controlled by a single type of topological objects. There are, however, some situations, still poorly understood, where two dual topological excitations fight to control the phase diagram and the transition. Finding experimental realizations of such cases is thus of considerable interest. We show here that this situation occurs in BaCo2V2O8, a spin-1/2 Ising-like quasi-one-dimensional antiferromagnet, when subjected to a uniform magnetic field transverse to the Ising axis. Using neutron scattering experiments, we measure a drastic modification of the quantum excitations beyond a critical value of the magnetic field. This quantum phase transition is identified, through a comparison with theoretical calculations, to be a transition between two different types of solitonic topological object, which are captured by different components of the dynamical structure factor.

  • 12.
    Faure, Quentin
    et al.
    Univ Grenoble Alpes, CEA, IRIG, MEM,MED, F-38000 Grenoble, France.;Univ Grenoble Alpes, Inst NEEL, F-38042 Grenoble, France..
    Takayoshi, Shintaro
    Max Planck Inst Phys Komplexer Syst, D-01307 Dresden, Germany.;Univ Geneva, Dept Quantum Matter Phys, CH-1211 Geneva, Switzerland..
    Simonet, Virginie
    Univ Grenoble Alpes, Inst NEEL, F-38042 Grenoble, France..
    Grenier, Beatrice
    Univ Grenoble Alpes, CEA, IRIG, MEM,MED, F-38000 Grenoble, France..
    Månsson, Martin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Paul Scherrer Inst, Lab Neutron Scattering & Imaging, CH-5232 Villigen, Switzerland.
    White, Jonathan S.
    Paul Scherrer Inst, Lab Neutron Scattering & Imaging, CH-5232 Villigen, Switzerland..
    Tucker, Gregory S.
    Paul Scherrer Inst, Lab Neutron Scattering & Imaging, CH-5232 Villigen, Switzerland.;Ecole Polytech Fed Lausanne, Inst Phys, Lab Quantum Magnetism, CH-1015 Lausanne, Switzerland..
    Ruegg, Christian
    Univ Geneva, Dept Quantum Matter Phys, CH-1211 Geneva, Switzerland.;Paul Scherrer Inst, Lab Neutron Scattering & Imaging, CH-5232 Villigen, Switzerland.;Paul Scherrer Inst, Neutrons & Muons Res Div, CH-1211 Villigen, Switzerland..
    Lejay, Pascal
    Univ Grenoble Alpes, Inst NEEL, F-38042 Grenoble, France..
    Giamarchi, Thierry
    Univ Geneva, Dept Quantum Matter Phys, CH-1211 Geneva, Switzerland..
    Petit, Sylvain
    Univ Paris Saclay, CEA Saclay, CNRS, Lab Leon Brillouin,CEA, F-91191 Gif Sur Yvette, France..
    Tomonaga-Luttinger Liquid Spin Dynamics in the Quasi-One-Dimensional Ising-Like Antiferromagnet BaCo2V2O82019In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 123, no 2, article id 027204Article in journal (Refereed)
    Abstract [en]

    Combining inelastic neutron scattering and numerical simulations, we study the quasi-one-dimensional Ising anisotropic quantum antiferromagnet BaCo2V2O8 in a longitudinal magnetic field. This material shows a quantum phase transition from a Neel ordered phase at zero field to a longitudinal incommensurate spin density wave at a critical magnetic field of 3.8 T. Concomitantly, the excitation gap almost closes and a fundamental reconfiguration of the spin dynamics occurs. These experimental results are well described by the universal Tomonaga-Luttinger liquid theory developed for interacting spinless fermions in one dimension. We especially observe the rise of mainly longitudinal excitations, a hallmark of the unconventional low-field regime in Ising-like quantum antiferromagnetic chains.

  • 13.
    Forslund, Ola Kenji
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Andreica, D.
    Sassa, Y.
    Nozaki, H.
    Umegaki, I.
    Nocerino, Elisabetta
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Jonsson, Viktor
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Tjernberg, Oscar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Guguchia, Z.
    Shermadini, Z.
    Khasanov, R.
    Isobe, M.
    Takagi, H.
    Ueda, Y.
    Sugiyama, J.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Magnetic phase diagram of K 2 Cr 8 O 16 clarified by high-pressure muon spin spectroscopy2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, no 1, article id 1141Article in journal (Refereed)
    Abstract [en]

    The K 2 Cr 8 O 16 compound belongs to a series of quasi-1D compounds with intriguing magnetic properties that are stabilized through a high-pressure synthesis technique. In this study, a muon spin rotation, relaxation and resonance (μ + SR) technique is used to investigate the pressure dependent magnetic properties up to 25 kbar. μ + SR allows for measurements in true zero applied field and hereby access the true intrinsic material properties. As a result, a refined temperature/pressure phase diagram is presented revealing a novel low temperature/high pressure (p C1 = 21 kbar) transition from a ferromagnetic insulating to a high-pressure antiferromagnetic insulator. Finally, the current study also indicates the possible presence of a quantum critical point at p C2 ~ 33 kbar where the magnetic order in K 2 Cr 8 O 16 is expected to be fully suppressed even at T = 0 K.

  • 14. Gao, S.
    et al.
    Guratinder, K.
    Stuhr, U.
    White, J. S.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics. Paul Scherrer Institute, Villigen, Switzerland.
    Roessli, B.
    Fennell, T.
    Tsurkan, V.
    Loidl, A.
    Ciomaga Hatnean, M.
    Balakrishnan, G.
    Raymond, S.
    Chapon, L.
    Garlea, V. O.
    Savici, A. T.
    Cervellino, A.
    Bombardi, A.
    Chernyshov, D.
    Rüegg, C.
    Haraldsen, J. T.
    Zaharko, O.
    Manifolds of magnetic ordered states and excitations in the almost Heisenberg pyrochlore antiferromagnet MgCr2 O42018In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 13, article id 134430Article in journal (Refereed)
    Abstract [en]

    In spinels ACr2O4(A=Mg, Zn), realization of the classical pyrochlore Heisenberg antiferromagnet model is complicated by a strong spin-lattice coupling: the extensive degeneracy of the ground state is lifted by a magneto-structural transition at TN=12.5 K. We study the resulting low-temperature low-symmetry crystal structure by synchrotron x-ray diffraction. The consistent features of x-ray low-temperature patterns are explained by the tetragonal model of Ehrenberg et al. [Pow. Diff. 17, 230 (2002)PODIE20885-715610.1154/1.1479738], while other features depend on sample or cooling protocol. A complex, partially ordered magnetic state is studied by neutron diffraction and spherical neutron polarimetry. Multiple magnetic domains of configuration arms of the propagation vectors k1=(12120),k2=(1012) appear. The ordered moment reaches 1.94(3) μB/Cr3+ for k1 and 2.08(3) μB/Cr3+ for k2, if equal amount of the k1 and k2 phases is assumed. The magnetic arrangements have the dominant components along the [110] and [1-10] diagonals and a smaller c component. We use inelastic neutron scattering to investigate the spin excitations, which comprise a mixture of dispersive spin waves propagating from the magnetic Bragg peaks and resonance modes centered at equal energy steps of 4.5 meV. We interpret these as acoustic and optical spin wave branches, but show that the neutron scattering cross sections of transitions within a unit of two corner-sharing tetrahedra match the observed intensity distribution of the resonances. The distinctive fingerprint of clusterlike excitations in the optical spin wave branches suggests that propagating excitations are localized by the complex crystal structure and magnetic orders.

  • 15.
    Grishin, Michael A.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Henrik S.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Månsson, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Electron structure and electron dynamics at InSb(111)2×2 semiconductor surface2003In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 76, no 3, p. 299-302Article in journal (Refereed)
    Abstract [en]

    The conduction band electronic structure and the electron dynamics of the clean InSb(111)2 x 2 surface have been studied by laser based pump-and-probe photoemission. The results are compared to earlier studies of the InSb(110) surface. It is found that both the energy location and the time dependence of the photoexcited structures are very similar for the two surfaces. This indicates that the dominant part of the photoemission signal in the conduction band region is due to excitations of electrons in the bulk region and that the surface electronic states play a minor role. The fast decay of the excited state, tau similar to 12 ps, indicates that diffusion of hot electrons into the bulk is an important mechanism.

  • 16.
    Grishin, Michael A.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Månsson, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Claesson, Thomas
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Henrik S.
    Optillion AB.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A bandgap surface state at the GaSb(001) surface observed by femtosecond laser pump-and-probe photoemission spectroscopyManuscript (Other academic)
  • 17.
    Grishin, Michael A.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Månsson, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Henrik S.
    Optillion AB.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A new two-dimensional angle-resolving multi-anode electron detector for femtosecond photoemission spectroscopyArticle in journal (Other academic)
  • 18.
    Grishin, Michael A.
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Karlsson, Henrik S.
    Optillion AB, Stockholm.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Anisotropy of electron structure at InAs(111) surfaces by laser pump-and-probe photoemission spectroscopy2005In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 574, no 1, p. 89-94Article in journal (Refereed)
    Abstract [en]

    The electronic structure and the electron dynamics of the clean InAs(111)A 2 x 2 and the InAs(111)B 1 x 1 surfaces have been studied by laser pump-and-probe photoemission spectroscopy. Normally unpopulated electron states above the valence band maximum (VBM) are filled on the InAs(111)A surface due to the conduction band pinning above the Fermi level (E-F). Accompanied by the downward band banding alignment, a charge accumulation layer is confined to the surface region creating a two dimensional electron gas (2DEG). The decay of the photoexcited carriers above the conduction band minimum (CBM) is originated by bulk states affected by the presence of the surface. No occupied states were found on the InAs(111)B 1 x 1 surface. This fact is suggested to be due to the surface stabilisation by the charge removal from the surface into the bulk. The weak photoemission intensity above the VBM on the (111)B surface is attributed to electron states trapped by surface defects. The fast decay of the photoexcited electron states on the (111)A and the (111)B surfaces was found to be tau(111A) less than or equal to 5 ps and tau(111B) less than or equal to 4ps, respectively. We suggest the diffusion of the hot electrons into the bulk is the decay mechanism. (

  • 19.
    Horio, M.
    et al.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Hauser, K.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Sassa, Y.
    Uppsala Univ, Dept Phys & Astron, SE-75121 Uppsala, Sweden..
    Mingazheva, Z.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Sutter, D.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Kramer, K.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Cook, A.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Nocerino, Elisabetta
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Forslund, Ola Kenji
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Tjernberg, Oscar
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Kobayashi, M.
    Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland..
    Chikina, A.
    Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland..
    Schroter, N. B. M.
    Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland..
    Krieger, J. A.
    Paul Scherrer Inst, Lab Muon Spin Spect, CH-5232 Villigen, Switzerland.;Swiss Fed Inst Technol, Lab Festkorperphys, CH-8093 Zurich, Switzerland..
    Schmitt, T.
    Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland..
    Strocov, V. N.
    Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland..
    Pyon, S.
    Univ Tokyo, Dept Adv Mat, Kashiwa, Chiba 2778561, Japan..
    Takayama, T.
    Univ Tokyo, Dept Adv Mat, Kashiwa, Chiba 2778561, Japan..
    Takagi, H.
    Univ Tokyo, Dept Adv Mat, Kashiwa, Chiba 2778561, Japan..
    Lipscombe, O. J.
    Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England..
    Hayden, S. M.
    Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England..
    Ishikado, M.
    CROSS, Tokai, Ibaraki 3191106, Japan..
    Eisaki, H.
    Natl Inst Adv Ind Sci & Technol, Elect & Photon Res Inst, Tsukuba 3058568, Japan..
    Neupert, T.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Matt, C. E.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland.;Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland.;Harvard Univ, Dept Phys, Cambridge, MA 02138 USA..
    Chang, J.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Three-Dimensional Fermi Surface of Overdoped La-Based Cuprates2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 121, no 7, article id 077004Article in journal (Refereed)
    Abstract [en]

    We present a soft x-ray angle-resolved photoemission spectroscopy study of overdoped high-temperature superconductors. In-plane and out-of-plane components of the Fermi surface are mapped by varying the photoemission angle and the incident photon energy. No k(z) dispersion is observed along the nodal direction, whereas a significant antinodal k(z) dispersion is identified for La-based cuprates. Based on a tight-binding parametrization, we discuss the implications for the density of states near the van Hove singularity. Our results suggest that the large electronic specific heat found in overdoped La2-xSrxCuO4 cannot be assigned to the van Hove singularity alone. We therefore propose quantum criticality induced by a collapsing pseudogap phase as a plausible explanation for observed enhancement of electronic specific heat.

  • 20.
    Horio, M.
    et al.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Matt, C. E.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland.;Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland.;Harvard Univ, Dept Phys, Cambridge, MA 02138 USA..
    Kramer, K.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Sutter, D.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Cook, A. M.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Sassa, Y.
    Uppsala Univ, Dept Phys & Astron, SE-75121 Uppsala, Sweden..
    Hauser, K.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Plumb, N. C.
    Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland..
    Shi, M.
    Paul Scherrer Inst, Swiss Light Source, CH-5232 Villigen, Switzerland..
    Lipscombe, O. J.
    Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England..
    Hayden, S. M.
    Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England..
    Neupert, T.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Chang, J.
    Univ Zurich, Phys Inst, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Two-dimensional type-II Dirac fermions in layered oxides2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 3252Article in journal (Refereed)
    Abstract [en]

    Relativistic massless Dirac fermions can be probed with high-energy physics experiments, but appear also as low-energy quasi-particle excitations in electronic band structures. In condensed matter systems, their massless nature can be protected by crystal symmetries. Classification of such symmetry-protected relativistic band degeneracies has been fruitful, although many of the predicted quasi-particles still await their experimental discovery. Here we reveal, using angle-resolved photoemission spectroscopy, the existence of two-dimensional type-II Dirac fermions in the high-temperature superconductor La1.77Sr0.23CuO4. The Dirac point, constituting the crossing of d(x2-y2) and d(z2) bands, is found approximately one electronvolt below the Fermi level (E-F) and is protected by mirror symmetry. If spin-orbit coupling is considered, the Dirac point degeneracy is lifted and the bands acquire a topologically non-trivial character. In certain nickelate systems, band structure calculations suggest that the same type-II Dirac fermions can be realised near EF.

  • 21. Klyushina, E. S.
    et al.
    Lake, B.
    Islam, A. T. M. N.
    Park, J. T.
    Schneidewind, A.
    Guidi, T.
    Goremychkin, E. A.
    Klemke, B.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Investigation of the spin-1 honeycomb antiferromagnet BaNi2V2O8 with easy-plane anisotropy2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 21, article id 214428Article in journal (Refereed)
    Abstract [en]

    The magnetic properties of the two-dimensional, S = 1 honeycomb antiferromagnet BaNi2V2O8 have been comprehensively studied using dc susceptibility measurements and inelastic neutron scattering techniques. The magnetic excitation spectrum is found to be dispersionless within experimental resolution between the honeycomb layers, while it disperses strongly within the honeycomb plane where it consists of two gapped spin-wave modes. The magnetic excitations are compared to linear spin-wave theory allowing the Hamiltonian to be determined. The first-and second-neighbor magnetic exchange interactions are antiferromagnetic and lie within the ranges 10.90 meV <= J(n) <= 13.35 meV and 0.85 meV <= J(nn) <= 1.65 meV, respectively. The interplane coupling J(out) is four orders of magnitude weaker than the intraplane interactions, confirming the highly two-dimensional magnetic behavior of this compound. The sizes of the energy gaps are used to extract the magnetic anisotropies and reveal substantial easy-plane anisotropy and a very weak in-plane easy-axis anisotropy. Together these results reveal that BaNi2V2O8 is a candidate compound for the investigation of vortex excitations and Berezinsky-Kosterliz-Thouless phenomenon.

  • 22. Matt, C. E.
    et al.
    Sutter, D.
    Cook, A. M.
    Sassa, Y.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Tjernberg, Oscar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Das, L.
    Horio, M.
    Destraz, D.
    Fatuzzo, C. G.
    Hauser, K.
    Shi, M.
    Kobayashi, M.
    Strocov, V. N.
    Schmitt, T.
    Dudin, P.
    Hoesch, M.
    Pyon, S.
    Takayama, T.
    Takagi, H.
    Lipscombe, O. J.
    Hayden, S. M.
    Kurosawa, T.
    Momono, N.
    Oda, M.
    Neupert, T.
    Chang, J.
    Direct observation of orbital hybridisation in a cuprate superconductor2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 972Article in journal (Refereed)
    Abstract [en]

    The minimal ingredients to explain the essential physics of layered copper-oxide (cuprates) materials remains heavily debated. Effective low-energy single-band models of the copper-oxygen orbitals are widely used because there exists no strong experimental evidence supporting multi-band structures. Here, we report angle-resolved photoelectron spectroscopy experiments on La-based cuprates that provide direct observation of a two-band structure. This electronic structure, qualitatively consistent with density functional theory, is parametrised by a two-orbital (d(x2-y2) and d(z2)) tight-binding model. We quantify the orbital hybridisation which provides an explanation for the Fermi surface topology and the proximity of the van-Hove singularity to the Fermi level. Our analysis leads to a unification of electronic hopping parameters for single-layer cuprates and we conclude that hybridisation, restraining d-wave pairing, is an important optimisation element for superconductivity.

  • 23. Muehlbauer, S.
    et al.
    Brandl, G.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Garst, M.
    Formation of incommensurate long-range magnetic order in the Dzyaloshinskii-Moriya antiferromagnet Ba-2 CuGe2O7 studied by neutron diffraction2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 13, article id 134409Article in journal (Refereed)
  • 24.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Adatoms, Quasiparticles & Photons: The Multifaceted World of Photoelectron Spectroscopy2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The experimental work presented in this thesis is based on a wide assortment of very advanced and highly sophisticated photoelectron spectroscopy (PES) techniques. The objective of the present study has been to reveal and understand the electronic structure and electron dynamics in a broad spectrum of materials, ranging from wide band gap oxides, via semiconductors along with metals, and finally high-temperature superconductors.

    The first part of the thesis concerns laser-based pump-and-probe PES. This unique experimental technique has permitted a study of the excited electronic structure and the electron dynamics of several semiconductor surfaces. An insight into details of the adatom to restatom charge-transfer of the Ge(111)c(2x8) surface is presented, as well as an estimate for the timescale in which the dynamic adatoms of the Ge(111):Sn(sqrt3xsqrt3)R30deg surface operate. Further results comprise a novel unoccupied surface state at the GaSb(001) surface as well as a time-resolved study of the charge accumulation layer at the InAs(111)A/B surfaces.

    In the second part, high-resolution synchrotron based angle-resolved PES (ARPES) data from the cuprate high-temperature superconductor La(2-x)Sr(x)CuO(4) (LSCO) is presented. This extensive study, reveals detailed information about how the Fermi surface and electronic excitations evolve with doping in the superconducting state. The results comprise support for a connection between high- and low-energy electronic responses, the characteristics of the superconducting gap, and indication of a quantum phase transition between two different superconducting phases.

    In the third group of experiments we move away from the two-dimensional systems and concentrate on fully three-dimensional compounds. By the use of soft x-ray ARPES it is possible to extract the three-dimensional electronic structure in a straightforward manner with increased k(perpendicular)-resolution. As a result the first high-quality ARPES data from Cu2O is presented, as well as a novel method for extracting the (real space) electron density by ARPES. These experiments clearly display the advantages of using soft x-ray ARPES. If the material and type of experiment is chosen wisely, the benefit of the increased k||-window and the free electron final state, surpass the drawbacks of decreased count-rate and inferior energy resolution. Finally we return to the high-temperature superconductors (NCCO & Nd-LSCO) and make use of the increased bulk-sensitivity. From an evident change in the shape of the Fermi surface when moving from low to high photon energies, the durface to bulk difference in electronic structure is highlighted.

  • 25.
    Månsson, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT).
    Finazzi, Marco
    Dallera, Claudia
    De Nadaï, Celine
    Brookes, Nicholas B.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT).
    Revealing the charge density in solidsManuscript (Other academic)
  • 26.
    Månsson, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT).
    Hayden, S. M.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT).
    Chang, Johan
    Pailhés, Stephane
    Shi, Ming
    Mesot, Joël
    Patthey, Luc
    Momono, Naoki
    Oda, Migaku
    Ido, Masayuki
    Experimental evidence of a quantum phase transition in La(2-x)Sr(x)CuO4()Manuscript (Other academic)
  • 27.
    Månsson, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Pailhés, Stephane
    Laboratory for Neutron Scattering, ETH Zürich.
    Chang, Johan
    Laboratory for Neutron Scattering, ETH Zürich.
    Mesot, Joël
    Laboratory for Neutron Scattering, ETH Zürich.
    Shi, Ming
    Swiss Light Source, Paul Scherrer Institut, Villigen.
    Patthey, Luc
    Swiss Light Source, Paul Scherrer Institut, Villigen.
    Momono, Naoki
    Department of Physics, Hokkaido University, Sapporo.
    Oda, Migaku
    Department of Physics, Hokkaido University, Sapporo.
    Ido, Masayuki
    Department of Physics, Hokkaido University, Sapporo.
    On-board sample cleaver2007In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 78, no 7, p. 076103-Article in journal (Refereed)
    Abstract [en]

    An on-board sample cleaver has been developed in order to cleave small and hard-to-cleave samples. To acquire good cleaves from rigid samples the alignment of the cleaving blade with respect to the internal crystallographic planes is crucial. To have the opportunity to mount the sample and align it to the blade ex situ has many advantages. The design presented has allowed us to cleave very tiny and rigid samples, e.g., the high-temperature superconductor La(2-x)SrxCuO4. Further, in this design the sample and the cleaver will have the same temperature, allowing us to cleave and keep the sample at low temperature. This is a big advantage over prior cleaver systems. As a result, better surfaces and alignments can be realized, which considerably simplifies and improves the experiments.

  • 28.
    Månsson, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Grishin, Michael A.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Karlsson, Henrik S.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Electronic structure and electron dynamics at the GaSb(001) surface studied by femtosecond pump-and-probe pulsed laser photoemission spectroscopy2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5308-5311Article in journal (Refereed)
    Abstract [en]

    Transiently excited electron states at the GaSb(001) surface have been studied by means of time- and angle-resolved photoemission spectroscopy based on a femtosecond laser system. A normally unpopulated surface electron state has been found at similar to 250 meV above the valence band maximum with a strong confinement at the center of the surface Brillouin zone. The lifetime of transiently excited carriers at the intergap surface states has been found to be similar to 11 ps, associated with rapid carrier diffusion.

  • 29.
    Månsson, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Grishin, Michael A.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Ultrafast electron dynamics and recombination at the Ge(111): Sn(root 3 X root 3)R30 degrees surface2008In: Surface Science Letters, ISSN 0039-6028, Vol. 602, no 5, p. L33-L37Article in journal (Refereed)
    Abstract [en]

    We present the first study revealing the electronic structure and electron dynamics of the excited adatom state at the Ge(111): Sn(root 3 x root 3)R30 degrees surface. By the use of time- and angle-resolved photoemission spectroscopy, the normally unoccupied electronic structure of the partly empty Sn adatom can be probed. From the angle-resolved data we conclude that the adatom electrons at the Ge:Sn surface are more delocalized than at the clean Ge(111)c(2 x 8) surface. A unique pump-and-probe technique, based on a pulsed femtosecond laser-system, has also allowed us to study the recombination process of the excited state. We connect the recombination process of the excited electrons to the coherent fluctuations of the Sn adatoms. As a result we present an estimate for the time between each collective and coherent adatom flip Delta t = 9 ps, i.e. an adatom switching frequency nu(SW) approximate to 0.1 THz. We find that our results, contrary to scanning tunneling microscopy measurements [F. Ronci, S. Colonna, S.D. Thorpe, A. Cricenti, G. Le Lay, Phys. Rev. Lett. 95 (2005) 156101], agree very well with values extracted from molecular dynamics simulations found in the literature [J. Avila, A. Mascaraque, E.G. Michel, M.C. Asensio, G. Le Lay, J. Ortega, R. Perez, F. Flores, Phys. Rev. Lett. 82 (1999) 442; D. Farias, W. Kaminski, J. Lobo, J. Ortega, E. Hulpke, R. Perez, F. Flores, E.G. Michel, Phys. Rev. Lett. 91 (2003) 16103].

  • 30.
    Månsson, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Grishin, Michael A.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Karlsson, Henrik S.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Le Lay, Guy
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Electronic structure and electron dynamics of delocalized adatom states at the Ge(111)c(2 x 8) surfaceIn: Physical Review B, ISSN 1098-0121Article in journal (Refereed)
  • 31. Nag, Abhishek
    et al.
    Middey, S.
    Bhowal, Sayantika
    Panda, S. K.
    Mathieu, Roland
    Orain, J. C.
    Bert, F.
    Mendels, P.
    Freeman, P. G.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
    Ronnow, H. M.
    Telling, M.
    Biswas, P. K.
    Sheptyakov, D.
    Kaushik, S. D.
    Siruguri, Vasudeva
    Meneghini, Carlo
    Sarma, D. D.
    Dasgupta, Indra
    Ray, Sugata
    Origin of the Spin-Orbital Liquid State in a Nearly J=0 Iridate Ba3ZnIr2O92016In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 116, no 9, article id 097205Article in journal (Refereed)
    Abstract [en]

    We show using detailed magnetic and thermodynamic studies and theoretical calculations that the ground state of Ba3ZnIr2O9 is a realization of a novel spin-orbital liquid state. Our results reveal that Ba3ZnIr2O9 with Ir5+ (5d(4)) ions and strong spin-orbit coupling (SOC) arrives very close to the elusive J = 0 state but each Ir ion still possesses a weak moment. Ab initio density functional calculations indicate that this moment is developed due to superexchange, mediated by a strong intradimer hopping mechanism. While the Ir spins within the structural Ir2O9 dimer are expected to form a spin-orbit singlet state (SOS) with no resultant moment, substantial frustration arising from interdimer exchange interactions induce quantum fluctuations in these possible SOS states favoring a spin-orbital liquid phase down to at least 100 mK.

  • 32.
    Nozaki, Hiroshi
    et al.
    Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan..
    Sakurai, Hiroya
    Natl Inst Mat Sci, Namiki 1-1, Tsukuba, Ibaraki 3050044, Japan..
    Ofer, Oren
    TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada..
    Ansaldo, Eduardo J.
    TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada..
    Brewer, Jess H.
    TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada.;Univ British Columbia, Dept Phys & Astron, Vancouver, BC V6T 1Z1, Canada..
    Chow, Kim H.
    Univ Alberta, Dept Phys, Edmonton, AB T6G 2J1, Canada..
    Pomjakushin, Vladimir
    Paul Scherrer Inst, Neutron Scattering Lab, CH-5232 Villigen, Switzerland..
    Keller, Lukas
    Paul Scherrer Inst, Neutron Scattering Lab, CH-5232 Villigen, Switzerland..
    Prsa, Krunoslav
    Univ Freiburg, Phys Inst, D-79104 Freiburg, Germany..
    Miwa, Kazutoshi
    Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan..
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Sugiyama, Jun
    Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan.;Japan Atom Energy Agcy, Adv Sci Res Ctr, Tokai, Ibaraki 3191195, Japan..
    Magnetic structure for NaCr2O4 analyzed by neutron diffraction and muon spin-rotation2018In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 551, p. 137-141Article in journal (Refereed)
    Abstract [en]

    We have investigated the magnetic ground state of a novel one-dimensional compound, NaCr2O4, in which Cr2O4 double chains, i.e. zig-zag chains are aligned parallel to the b-axis, by means of both muon-spin rotation and relaxation (mu+SR) and neutron diffraction (ND) measurements. The mu+SR results reveal the formation of static antiferromagnetic order below Neel temperature (T-N = 124 K). The ND measurements also demonstrate the appearance of magnetic Bragg peaks with the propagation vector (k) over right arrow = (1, 0, 1) below T-N. Combined analyses of the mu+SR and ND data clarify that the Cr moments in each zig-zag chain are aligned ferromagnetically along the c-axis, whereas antiferromagnetically along the alpha-axis between the adjacent zig-zag chains.

  • 33.
    Palmgren, Pål
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Önsten, Anneli
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Agnarsson, Björn
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Band bending and structure dependent HOMO energy at the ZnO(0001)-titanyl phthalocyanine interface2007In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 601, no 18, p. 4222-4226Article in journal (Refereed)
    Abstract [en]

    We have investigated the initial stages of titanyl phthalocyanine (TiOPc) growth on single crystalline ZnO(0 0 0 1). This organic-semiconductor interface is self-organizing as a 2 x 1 pattern appears in a low energy electron diffraction upon deposition of the molecules. To achieve this pattern, the TiOPc is suggested to adsorb standing with the edge of the molecule along the substrate atomic rows. Photoelectron spectroscopy is used to further analyze the interface; a relatively large upwards band bending amounting to 0.5 eV is found and a splitting of the molecules highest occupied molecular orbital occurs after thermal treatment, indicating that the molecules are lying down.

  • 34. Razzoli, E.
    et al.
    Matt, C. E.
    Sassa, Y.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF. Ecole Polytech Fed Lausanne, Switzerland.
    Tjernberg, Oscar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Drachuck, G.
    Monomo, M.
    Oda, M.
    Kurosawa, T.
    Huang, Y.
    Plumb, N. C.
    Radovic, M.
    Keren, A.
    Patthey, L.
    Mesot, J.
    Shi, M.
    Rotation symmetry breaking in La2-xSrxCuO4 revealed by angle-resolved photoemission spectroscopy2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 22, article id 224504Article in journal (Refereed)
    Abstract [en]

    Using angle-resolved photoemission spectroscopy it is revealed that in the vicinity of optimal doping the electronic structure of La2-x SrxCuO4 cuprate undergoes an electronic reconstruction associated with a wave vector q(a) = (pi, 0). The reconstructed Fermi surface and folded band are distinct to the shadow bands observed in BSCCO cuprates and in underdoped La2-xSrxCuO4 with x <= 0.12, which shift the primary band along the zone diagonal direction. Furthermore, the folded bands appear only with q(a) = (pi, 0) vector, but not with q(b) = (0, pi). We demonstrate that the absence of q(b) reconstruction is not due to thematrix-element effects in the photoemission process, which indicates the fourfold symmetry is broken in the system.

  • 35.
    Sassa, Y.
    et al.
    Uppsala Univ, Dept Phys & Astron, Box 530, S-75121 Uppsala, Sweden.;Paul Scherrer Inst, Lab Neutron Scattering & Imaging, CH-5232 Villigen, Switzerland..
    Månsson, Martin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Forslund, Ola K
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Tjernberg, Oscar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Pomjakushin, V.
    Paul Scherrer Inst, Lab Neutron Scattering & Imaging, CH-5232 Villigen, Switzerland..
    Ofer, O.
    TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada..
    Ansaldo, E. J.
    TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada..
    Brewer, J. H.
    TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada..
    Umegaki, I.
    Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan..
    Higuchi, Y.
    Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan..
    Ikedo, Y.
    Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan.;KEK, Muon Sci Lab, Tsukuba, Ibaraki 3050801, Japan..
    Nozaki, H.
    Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan..
    Harada, M.
    Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan..
    Watanabe, I.
    RIKEN Nishina Ctr, Adv Meson Sci Lab, 2-1 Hirosawa, Wako, Saitama 3510198, Japan..
    Sakurai, H.
    Natl Inst Mat Sci, Tsukuba, Ibaraki 3050044, Japan..
    Sugiyama, J.
    Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan..
    The metallic quasi-1D spin-density-wave compound NaV2O4 studied by angle-resolved photoelectron spectroscopy2018In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 79-83Article in journal (Refereed)
    Abstract [en]

    Angle-resolved photoelectron spectroscopy has been used to follow the valence band and near Fermi edge electronic band structure in the quasi-1D compound NaV2O4. In this current study we have acquired the very first high-quality, high-resolution ARPES data from this material. Our data clearly reveal two distinct dispersive bands that cross the Fermi level at different k(F). This is a clear signature that the electronic properties of this material is affected by the presence of a mixed valence state on the different vanadium chains and possibly also the low-temperature magnetic spin order.

  • 36. Shi, M.
    et al.
    Bendounan, A.
    Razzoli, E.
    Rosenkranz, S.
    Norman, M. R.
    Campuzano, J. C.
    Chang, J.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Sassa, Y.
    Claesson, Tomas
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Patthey, L.
    Momono, N.
    Oda, M.
    Ido, M.
    Guerrero, S.
    Mudry, C.
    Mesot, J.
    Spectroscopic evidence for preformed Cooper pairs in the pseudogap phase of cuprates2009In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 88, no 2Article in journal (Refereed)
    Abstract [en]

    Angle-resolved photoemission on underdoped La1.895Sr0.105CuO4 reveals that in the pseudogap phase, the dispersion has two branches located above and below the Fermi level with a minimum at the Fermi momentum. This is characteristic of the Bogoliubov dispersion in the superconducting state. We also observe that the superconducting and pseudogaps have the same d-wave form with the same amplitude. Our observations provide direct evidence for preformed Cooper pairs, implying that the pseudogap phase is a precursor to superconductivity.

  • 37.
    Shi, Ming
    et al.
    Swiss Light Source, Paul Scherrer Institute, Villigen.
    Chang, Johan
    Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, Villigen .
    Pailhés, Stephane
    Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, Villigen .
    Norman, M. R.
    Materials Science Division, Argonne National Laboratory, Argonne.
    Campuzano, J. C.
    Materials Science Division, Argonne National Laboratory, Argonne.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Bendounan, Azzedin
    Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, Villigen .
    Patthey, Luc
    Swiss Light Source, Paul Scherrer Institute, Villigen.
    Momono, Naoki
    Department of Physics, Hokkaido University, Sapporo.
    Oda, Migaku
    Department of Physics, Hokkaido University, Sapporo.
    Ido, Masayuki
    Department of Physics, Hokkaido University, Sapporo.
    Mudry, C.
    Condensed Matter Theory Group, Paul Scherrer Institute, Villigen.
    Mesot, Joël
    Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, Villigen .
    Coherent d-wave superconducting gap in underdoped La2-xSrxCuO4 by angle-resolved photoemission spectroscopy2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 101, no 4, p. 047002-Article in journal (Refereed)
    Abstract [en]

    We present angle-resolved photoemission spectroscopy data on moderately underdoped La1.855Sr0.145CuO4 at temperatures below and above the superconducting transition temperature. Unlike previous studies of this material, we observe sharp spectral peaks along the entire underlying Fermi surface in the superconducting state. These peaks trace out an energy gap that follows a simple d-wave form, with a maximum superconducting gap of 14 meV. Our results are consistent with a single gap picture for the cuprates. Furthermore our data on the even more underdoped sample La1.895Sr0.105CuO4 also show sharp spectral peaks, even at the antinode, with a maximum superconducting gap of 26 meV.

  • 38. Skoulatos, M.
    et al.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Paul Scherrer Institute, Switzerland; École Polytechnique Fédérale de Lausanne, Switzerland.
    Fiolka, C.
    Kramer, K. W.
    Schefer, J.
    White, J. S.
    Ruegg, Ch.
    Dimensional reduction by pressure in the magnetic framework material CuF2(D2O)(2)( pyz): From spin-wave to spinon excitations2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 2, article id 020414Article in journal (Refereed)
    Abstract [en]

    Metal organic magnets have enormous potential to host a variety of electronic and magnetic phases that originate from a strong interplay between the spin, orbital, and lattice degrees of freedom. We control this interplay in the quantum magnet CuF2(D2O)(2)( pyz) by using high pressure to drive the system through structural and magnetic phase transitions. Using neutron scattering, we show that the low pressure state, which hosts a two-dimensional square lattice with spin-wave excitations and a dominant exchange coupling of 0.89 meV, transforms at high pressure into a one-dimensional spin chain hallmarked by a spinon continuum and a reduced exchange interaction of 0.43 meV. This direct microscopic observation of a magnetic dimensional crossover as a function of pressure opens up new possibilities for studying the evolution of fractionalised excitations in low-dimensional quantum magnets and eventually pressure-controlled metal-insulator transitions.

  • 39. Soda, Minoru
    et al.
    Hayashida, Shohei
    Roessli, Bertrand
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Paul Scherrer Inst.
    White, Jonathan S.
    Matsumoto, Masashige
    Shiina, Ryousuke
    Masuda, Takatsugu
    Continuous control of local magnetic moment by applied electric field in multiferroics Ba2CoGe2O72016In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 94, no 9, article id 094418Article in journal (Refereed)
    Abstract [en]

    Ba2CoGe2O7 exhibits a collinear-antiferromagnetic structure with the easy axis along < 100 > directions and an antiferroelectric order with the polarization axis along the [001] direction. By applying the electric field the magnetic moment rotates from < 100 > to [110] directions and, simultaneously, the antiferroelectric state changes to the ferroelectric state gradually. This magnetoelectric effect, i.e., continuous control of the local magnetic moment by the electric field, is quantitatively explained by the Hamiltonian including the dielectric energy.

  • 40. Sugiyama, J.
    et al.
    Umegaki, I.
    Matsumoto, M.
    Miwa, K.
    Nozaki, H.
    Higuchi, Y.
    Noritake, T.
    Forslund, Ola Kenji
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Cottrell, S. P.
    Koda, A.
    Ansaldo, E. J.
    Brewer, J. H.
    Desorption reaction in MgH 2 studied with in situ μ + SR2019In: Sustainable Energy and Fuels, ISSN 2398-4902, Vol. 3, no 4, p. 956-964Article in journal (Refereed)
    Abstract [en]

    In order to study the mechanism determining the desorption temperature (T d ) of hydrogen storage materials, we have measured positive muon spin rotation and relaxation (μ + SR) in MgH 2 over a wide temperature range including its T d . The pressure in the sample cell due to desorbed H 2 was measured in parallel with the μ + SR measurements under static conditions. Such in situ μ + SR measurements revealed that hydrogen starts to diffuse in MgH 2 well below T d . This indicates the important role of hydrogen diffusion in accelerating the desorption reaction by removing the reaction product, i.e. H 2 , from the reaction system.

  • 41. Sugiyama, Jun
    et al.
    Nozaki, Hiroshi
    Harada, Masashi
    Higuchi, Yuki
    Sakurai, Hiroya
    Ansaldo, Eduardo J.
    Brewer, Jess H.
    Keller, Lukas
    Pomjakushin, Vladimir
    Mansson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Magnetic ground state of novel zigzag chain compounds, NaCr2O4 and Ca1-xNaxCr2O4, determined with muons and neutrons2015In: 20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015, Elsevier, 2015, p. 868-875Conference paper (Refereed)
    Abstract [en]

    The magnetic nature of a novel one-dimensional compound NaCr2O4 with zigzag CrO2 chains has been studied by muon spin rotation and relaxation (mu+SR) and neutron diffraction (ND). It is found that NaCr2O4 undergoes an antiferromagnetic transition at T-N = 125 K, below which the Cr moments in each zigzag chain align ferromagnetically along the c-axis but antiferromagnetically along the a-axis between adjacent zigzag chains. For the solid solution system Ca1-xNaxCr2O4, mu+SR measurements reveal the evolution of a complex magnetic order with increasing Ca content (1 - x), which finally enters into an incommensurate AF ordered state below T-N = 21 for CaCr2O4.

  • 42. Sugiyama, Jun
    et al.
    Nozaki, Hiroshi
    Harada, Masashi
    Umegaki, Izumi
    Higuchi, Yuki
    Miwa, Kazutoshi
    Imai, Masaki
    Michioka, Chishiro
    Yoshimura, Kazuyoshi
    Ansaldo, Eduardo J.
    Brewer, Jess H.
    Andreica, Daniel
    Baines, Christopher
    Mansson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Magnetic phases in Sr1-xCaxCo2P2 studied by mu+SR2015In: 20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015, Elsevier, 2015, p. 426-434Conference paper (Refereed)
    Abstract [en]

    In order to elucidate the dependence of the magnetic ground state on the Ca content (x) in Sr1-xCaxCo2P2 (0 <= x <= 1, ThCr2Si2-type structure), we have performed muon spin rotation and relaxation (mu+SR) experiments on Sr1-xCaxCo2P2 powder samples mainly in a zero applied field. The end member compound, SrCo2P2, is found to be paramagnetic down to 19 mK. As x increases, such a paramagnetic ground state is observed down to 1.8 K until x = 0.45. Then, as x increases further, a short-range antiferromagnetic (AF) ordered phase appears at low temperatures for 0.48 <= x <= 0.75, and finally, a long-range AF ordered phase is stabilized for x > 0.75. The internal magnetic field of the other end member compound, CaCo2P2, is well consistent with that of the A-type AF order state, which was proposed from neutron scattering experiments. The phase diagram determined with mu+SR is different from that proposed by macroscopic measurements. For an isostructural compound, LaCo2P2, static magnetic order is found to be formed below similar to 130 K.

  • 43. Sugiyama, Jun
    et al.
    Nozaki, Hiroshi
    Umegaki, Izumi
    Harada, Masashi
    Higuchi, Yuki
    Miwa, Kazutoshi
    Ansaldo, Eduardo J.
    Brewer, Jess H.
    Imai, Masaki
    Michioka, Chishiro
    Yoshimura, Kazuyoshi
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Variation of magnetic ground state of Sr1-xCaxCo2P2 determined with mu(+) SR2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 14, article id 144423Article in journal (Refereed)
    Abstract [en]

    In order to study the variation of a microscopic internal magnetic field with the Ca content (x), we have systematically measured muon-spin rotation and relaxation (mu+SR) spectra for Sr1-xCaxCo2P2 (0 <= x <= 1) powder samples mainly in a zero external field. As x increases from 0, a Pauli-paramagnetic phase is observed even at the lowest T measured (1.8 K) until x = 0.45; then, a short-range antiferromagnetic (AF) ordered phase appears for 0.48 <= x <= 0.75, and finally a long-range AF ordered phase is stabilized for x >= 0.75. The evolution of the magnetic order is connected to the shrinking of the c-axis length as a function of x, which naturally enhances the AF interaction between the two adjacent Co planes.

  • 44. Sugiyama, Jun
    et al.
    Nozaki, Hiroshi
    Umegaki, Izumi
    Miwa, Kazutoshi
    Higemoto, Wataru
    Ansaldo, Eduardo J.
    Brewer, Jess H.
    Sakurai, Hiroya
    Isobe, Masahiko
    Takagi, Hidenori
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Magnetism of the A-site ordered perovskites CaCu3Cr4O12 and LaCu3Cr4O122018In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 2, article id 024416Article in journal (Refereed)
    Abstract [en]

    The microscopic magnetic nature of the A-site ordered chromium perovskites CaCu3Cr4O12 and LaCu3Cr4O12 and their solid-solution system, Ca1-x LaxCu3Cr4O12, with x = 0.2, 0.4, and 0.8, has been studied with muon spin rotation and relaxation (mu+SR) measurements down to 2 K using a powder sample. For CaCu3Cr4O12, mu+SR revealed the formation of static antiferromagnetic (AF) order below 122 K (=T-N), although magnetization measurements showed a very small change at T-N. Analyses of the internal magnetic field H-int at the muon sites, predicted with first-principles calculations, suggested G-type AF order as a ground state. For LaCu3Cr4O12 with T-N = 225 K, mu+SR also supported the presence of aG-type AF ordered state, which was recently proposed based on neutron diffraction measurements. However, the ordered Cr moments were found to change the direction at around 10 K. For Ca1-xLaxCu3Cr4O12, both T-N and H-int at 2 K increase monotonically with x.

  • 45. Sugiyama, Jun
    et al.
    Nozaki, Hiroshi
    Umegaki, Izumi
    Mukai, Kazuhiko
    Miwa, Kazutoshi
    Shiraki, Susumu
    Hitosugi, Taro
    Suter, Andreas
    Prokscha, Thomas
    Salman, Zaher
    Lord, James S.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Li-ion diffusion in Li4Ti5O12 and LiTi2O4 battery materials detected by muon spin spectroscopy2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 1, article id 014417Article in journal (Refereed)
    Abstract [en]

    Lithium diffusion in spinel Li4Ti5O12 and LiTi2O4 compounds for future battery applications has been studied with muon spin relaxation (mu+SR). Measurements were performed on both thin-film and powder samples in the temperature range between 25 and 500 K. For Li4Ti5O12 and above about similar to 200 K, the field distribution width (Delta) is found to decrease gradually, while the field fluctuation rate (nu) increases exponentially with temperature. For LiTi2O4, on the contrary, the Delta(T) curve shows a steplike decrease at similar to 350 K, around which the nu(T) curve exhibits a local maximum. These behaviors suggest that Li+ starts to diffuse above around 200 K for both spinels. Assuming a jump diffusion of Li+ at the tetrahedral 8a site to the vacant octahedral 16c site, diffusion coefficients of Li+ at 300 K in the film samples are estimated as (3.2 +/- 0.8) x 10(-11) cm(2)/s for Li4Ti5O12 and (3.6 +/- 1.1) x 10(-11) cm(2)/s for LiTi2O4. Further, some small differences are found in both thermal activation energies and Li-ion diffusion coefficients between the powder and thin-film samples.

  • 46. Sugiyama, Jun
    et al.
    Umegaki, Izumi
    Andreica, Daniel
    Baines, Christopher
    Amato, Alex
    Guignard, Marie
    Delmas, Claude
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Unveiled magnetic transition in Na battery material: mu+SR study of P2-Na0.5VO22015In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 24, p. 18531-18537Article in journal (Refereed)
    Abstract [en]

    We have investigated the microscopic magnetic nature of a novel Na battery material, P2-Na0.5VO2, in which V ions form a two-dimensional triangular lattice, by means of muon-spin rotation and relaxation (mu+SR) measurements down to 50 mK. Although magnetization measurements indicated the presence of an antiferromagnetic transition at 13 K, the internal magnetic field due to the formation of magnetic order appears not at 13 K but at 2 K. Furthermore, the magnetic order is found to have a wide field distribution even at 50 mK. Such wide field distribution is reasonably explained by a combination of multiple muon sites and the formation of a long-range magnetic order, while the reliable spin structure is still unknown.

  • 47. Umegaki, Izumi
    et al.
    Kawauchi, Shigehiro
    Sawada, Hiroshi
    Nozaki, Hiroshi
    Higuchi, Yuki
    Miwa, Kazutoshi
    Kondo, Yasuhito
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Telling, Mark
    Coomer, Fiona C.
    Cottrell, Stephen P.
    Sasaki, Tsuyoshi
    Kobayashi, Tetsuro
    Sugiyama, Jun
    Li-ion diffusion in Li intercalated graphite C6Li and C12Li probed by mu+SR2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 29, p. 19058-19066Article in journal (Refereed)
    Abstract [en]

    In order to study a diffusive behavior of Li+ in Li intercalated graphites, we have measured muon spin relaxation (mu+SR) spectra for C6Li and C12Li synthesized with an electrochemical reaction between Li and graphite in a Li-ion battery. For both compounds, it was found that Li+ ions start to diffuse above 230 K and the diffusive behavior obeys a thermal activation process. The activation energy (E-a) for C6Li is obtained as 270(5) meV, while E-a = 170(20) meV for C12Li. Assuming a jump diffusion of Li+ in the Li layer of C6Li and C12Li, a self-diffusion coefficient D-Li at 310 K was estimated as 7.6(3) x 10(-11) (cm(2) s(-1)) in C6Li and 14.6(4) x 10(-11) (cm(2) s(-1)) in C12Li.

  • 48.
    Weissenrieder, Jonas
    et al.
    KTH, Superseded Departments, Physics.
    Göthelid, Mats
    KTH, Superseded Departments, Physics.
    Månsson, Martin
    KTH, Superseded Departments, Physics.
    von Schenck, Henrik
    KTH, Superseded Departments, Physics.
    Tjernberg, Oscar
    KTH, Superseded Departments, Physics.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Physics.
    Oxygen structures on Fe(110)2003In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 527, no 03-jan, p. 163-172Article in journal (Refereed)
    Abstract [en]

    The adsorption of oxygen on a Fe(110) single crystal has been studied by means of high resolution photoelectron spectroscopy (HRPES) and scanning tunneling microscopy (STM). Core level spectra were analyzed in detail on both clean and adsorbate covered surfaces. A shoulder on the high binding energy side of the Fe 2p core level indicates a structure comprising multiple components interpreted as an exchange split of the final state due to interaction between the 2p and 3d electrons. After adsorption of oxygen, (2 x 5), (2 x 2) and (3 x 1) reconstructions were observed with atomically resolved STM. The iron surface was further exposed to gradually higher doses of oxygen. Deconvolution of the O 1s HRPES spectra revealed two components separated approximately by 0.4 eV. The component at lower binding energy dominates at low coverage, while the high binding energy component increases in intensity with increasing O coverage. The formation of oxides was observed in the Fe 2p spectrum in the region between 708 and 710 eV. Further, well ordered iron oxides were grown by exposure to oxygen at 250 degreesC. The O 1s core level contained a single component with a binding energy similar to that of the high energy component in the just discussed O 1s spectrum. Low energy electron diffraction and STM images of this structure showed a large moire pattern with a 22.1 Angstrom x 30.9 Angstrom unit cell.

  • 49. Zhu, Jian-Xin
    et al.
    Janoschek, Marc
    Chaves, D. S.
    Cezar, J. C.
    Durakiewicz, Tomasz
    Ronning, Filip
    Sassa, Yasmine
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Scott, B. L.
    Wakeham, N.
    Bauer, Eric D.
    Thompson, J. D.
    Electronic correlation and magnetism in the ferromagnetic metal Fe3GeTe22016In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 14, article id 144404Article in journal (Refereed)
    Abstract [en]

    Motivated by the search for design principles of rare-earth-free strong magnets, we present a study of electronic structure and magnetic properties of the ferromagnetic metal Fe3GeTe2 within the local-density approximation (LDA) of the density-functional theory, and its combination with dynamical mean-field theory (DMFT). To compare these calculations, we measure magnetic and thermodynamic properties as well as x-ray magnetic circular dichroism and the photoemission spectrum of single-crystal Fe3GeTe2. We find that the experimentally determined Sommerfeld coefficient is enhanced by an order of magnitude with respect to the LDA value. This enhancement can be partially explained by LDA+DMFT. In addition, the inclusion of dynamical electronic correlation effects provides the experimentally observed magnetic moments, and the spectral density is in better agreement with photoemission data. These results establish the importance of electronic correlations in this ferromagnet.

  • 50.
    Önsten, Anneli
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Muro, Takayuki
    Japan Synchrotron Radiation Research Institute (JASRI).
    Matsushita, Tomohiro
    Japan Synchrotron Radiation Research Institute (JASRI).
    Nakamura, Tetsuya
    Japan Synchrotron Radiation Research Institute (JASRI).
    Kinoshita, Toyohiko
    Japan Synchrotron Radiation Research Institute (JASRI).
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Probing the valence band structure of Cu2O using high-energy angle-resolved photoelectron spectroscopy2007In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 76, no 11, p. 115127-1-115127-7Article in journal (Refereed)
    Abstract [en]

    We present angle-resolved photoemission data along the M-Gamma-M direction from a Cu2O(111) single crystal, collected at high photon energies (h nu=619 and 891 eV) and T=100 K. Because of the high photon energies and effective background subtraction, our data give a clear picture of the bulk band structure. The results confirm the existence of a hybridized Cu 3d-Cu 4s state located between the two main Cu 3d and O 2p band regions. Several theoretical studies have predicted the existence of this band, but until now it has not been detected in any photoemission measurements. The experimentally derived band structure is compared to local density approximation calculations with and without the Hubbard potential U. The clear band dispersion in our experimental data has enabled us to extract a refined Hubbard U value, which makes it possible to achieve a better agreement between theoretically calculated bands and experimental data.

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