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  • 1.
    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.

  • 2.
    Duan, Yu-Xia
    et al.
    Cent S Univ, Sch Phys & Elect, Changsha 410083, Hunan, Peoples R China..
    Zhang, Cheng
    Cent S Univ, Sch Phys & Elect, Changsha 410083, Hunan, Peoples R China..
    Rusz, Jan
    Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden..
    Oppeneer, Peter M.
    Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden..
    Durakiewicz, Tomasz
    Marie Curie Sklodowska Univ, Lnstitute Phys, PL-20031 Lublin, Poland..
    Sassa, Yasmine
    Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden.;Chalmers Univ Technol, Dept Phys, S-41296 Gothenburg, Sweden..
    Tjernberg, Oscar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Berntsen, Magnus H.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Wu, Fan-Ying
    Cent S Univ, Sch Phys & Elect, Changsha 410083, Hunan, Peoples R China..
    Zhao, Yin-Zou
    Cent S Univ, Sch Phys & Elect, Changsha 410083, Hunan, Peoples R China..
    Song, Jiao-Jiao
    Cent S Univ, Sch Phys & Elect, Changsha 410083, Hunan, Peoples R China..
    Wu, Qi-Yi
    Cent S Univ, Sch Phys & Elect, Changsha 410083, Hunan, Peoples R China..
    Luo, Yang
    Cent S Univ, Sch Phys & Elect, Changsha 410083, Hunan, Peoples R China..
    Bauer, Eric D.
    Los Alamos Natl Lab, Condensed Matter & Magnet Sci Grp, Los Alamos, NM 87545 USA..
    Thompson, Joe D.
    Los Alamos Natl Lab, Condensed Matter & Magnet Sci Grp, Los Alamos, NM 87545 USA..
    Meng, Jian-Qiao
    Cent S Univ, Sch Phys & Elect, Changsha 410083, Hunan, Peoples R China.;Hunan Normal Univ, SICQEA, Changsha 410081, Hunan, Peoples R China..
    Crystal electric field splitting and f-electron hybridization in heavy-fermion CePt2In72019In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 8, article id 085141Article in journal (Refereed)
    Abstract [en]

    We use high-resolution angle-resolved photoemission spectroscopy to investigate the electronic structure of the antiferromagnetic heavy fermion compound CePt2In7, which is amember of the CeIn3-derived heavy fermion material family. Weak hybridization among 4f electron states and conduction bands was identified in CePt2In7 at low temperature much weaker than that in the other heavy fermion compounds like CeIrIn5 and CeRhIn5. The Ce 4f spectrum shows fine structures near the Fermi energy, reflecting the crystal electric field splitting of the 4f(5/2)(1) and 4f(7/2)(1) states. Also, we find that the Fermi surface has a strongly three-dimensional topology, in agreement with density-functional theory calculations.

  • 3.
    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.

  • 4.
    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.

  • 5.
    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.

  • 6. 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.

  • 7.
    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.

  • 8.
    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.

  • 9. 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.

  • 10.
    Kobayashi, Shintaro
    et al.
    Nagoya Univ, Grad Sch Engn, Dept Appl Phys, Nagoya, Aichi 4648603, Japan.;SPring 8, Japan Synchrotron Radiat Res Inst, 1-1-1 Kouto, Sayo 6795198, Japan..
    Katayama, Naoyuki
    Nagoya Univ, Grad Sch Engn, Dept Appl Phys, Nagoya, Aichi 4648603, Japan..
    Manjo, Taishun
    Nagoya Univ, Grad Sch Engn, Dept Appl Phys, Nagoya, Aichi 4648603, Japan..
    Ueda, Hiroaki
    Kyoto Univ, Grad Sch Sci, Dept Chem, Kyoto 6068502, Japan..
    Michioka, Chishiro
    Kyoto Univ, Grad Sch Sci, Dept Chem, Kyoto 6068502, Japan..
    Sugiyama, Jun
    Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan.;CROSS Neutron Sci & Technol Ctr, Tokai, Ibaraki 3191106, Japan..
    Sassa, Yasmine
    Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden.;Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden..
    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.
    Yoshimura, Kazuyoshi
    Kyoto Univ, Grad Sch Sci, Dept Chem, Kyoto 6068502, Japan.;Kyoto Univ, Res Ctr Low Temp & Mat Sci, Kyoto 6068501, Japan..
    Sawa, Hiroshi
    Nagoya Univ, Grad Sch Engn, Dept Appl Phys, Nagoya, Aichi 4648603, Japan..
    Linear Trimer Formation with Antiferromagnetic Ordering in 1T-CrSe2 Originating from Peierls-like Instabilities and Interlayer Se-Se Interactions2019In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, no 21, p. 14304-14315Article in journal (Refereed)
    Abstract [en]

    Anomalous successive structural transitions in layered 1T-CrSe2 with an unusual Cr4+ valency were investigated by synchrotron X-ray diffraction. 1T-CrSe2 exhibits dramatic structural changes in in-plane Cr-Cr and interlayer Se-Se distances, which originate from two interactions: (i) in-plane Cr-Cr interactions derived from Peierls-like trimerization instabilities on the orbitally assisted one-dimensional chains and (ii) interlayer Se-Se interactions through p-p hybridization. As a result, 1T-CrSe2 has the unexpected ground state of an antiferromagnetic metal with multiple Cr linear trimers with three-center-two-electron sigma bonds. Interestingly, partial substitution of Se for S atoms in 1T-CrSe2 changes the ground state from an antiferromagnetic metal to an insulator without long-range magnetic ordering, which is due to the weakening of interlayer interactions between anions. The unique low-temperature structures and electronic states of this system are determined by the competition and cooperation of in-plane Cr-Cr and interlayer Se-Se interactions.

  • 11. 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.

  • 12. 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)
  • 13.
    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.

  • 14. 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.

  • 15.
    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.

  • 16. 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.

  • 17. 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.

  • 18. 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.

  • 19. 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.

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