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Publications (10 of 65) Show all publications
Polley, C. M., Buczko, R., Forsman, A., Dziawa, P., Szczerbakow, A., Rechcinski, R., . . . Balasubramanian, T. (2018). Fragility of the Dirac Cone Splitting in Topological Crystalline Insulator Heterostructures. ACS Nano, 12(1), 617-626
Open this publication in new window or tab >>Fragility of the Dirac Cone Splitting in Topological Crystalline Insulator Heterostructures
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2018 (English)In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 1, p. 617-626Article in journal (Refereed) Published
Abstract [en]

The "double Dirac cone" 2D topological interface states found on the (001) faces of topological crystalline insulators such as Pb1-xSnxSe feature degeneracies located away from time reversal invariant momenta and are a manifestation of both mirror symmetry protection and valley interactions. Similar shifted degeneracies in 1D interface states have been highlighted as a potential basis for a topological transistor, but realizing such a device will require a detailed understanding of the intervalley physics involved. In addition, the operation of this or similar devices outside of ultrahigh vacuum will require encapsulation, and the consequences of this for the topological interface state must be understood. Here we address both topics for the case of 2D surface states using angle-resolved photoemission spectroscopy. We examine bulk Pb1-xSnxSe(001) crystals overgrown with PbSe, realizing trivial/topological heterostructures. We demonstrate that the valley interaction that splits the two Dirac cones at each (X) over bar is extremely sensitive to atomic-scale details of the surface, exhibiting non-monotonic changes as PbSe deposition proceeds. This includes an apparent total collapse of the splitting for sub-monolayer coverage, eliminating the Lifshitz transition. For a large overlayer thickness we observe quantized PbSe states, possibly reflecting a symmetry confinement mechanism at the buried topological interface.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
Keywords
angle-resolved photoemission spectroscopy (ARPES), topological crystalline insulator, topological heterostructure, valley splitting, quantum confinement
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-222439 (URN)10.1021/acsnano.7b07502 (DOI)000423495200066 ()29251489 (PubMedID)2-s2.0-85042198890 (Scopus ID)
Note

QC 20180219

Available from: 2018-02-19 Created: 2018-02-19 Last updated: 2018-05-24Bibliographically approved
Sassa, Y., Månsson, M., Forslund, O. K., Tjernberg, O., Pomjakushin, V., Ofer, O., . . . Sugiyama, J. (2018). The metallic quasi-1D spin-density-wave compound NaV2O4 studied by angle-resolved photoelectron spectroscopy. Journal of Electron Spectroscopy and Related Phenomena, 224, 79-83
Open this publication in new window or tab >>The metallic quasi-1D spin-density-wave compound NaV2O4 studied by angle-resolved photoelectron spectroscopy
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2018 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 79-83Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-228150 (URN)10.1016/j.elspec.2017.05.010 (DOI)000428825400013 ()2-s2.0-85020828289 (Scopus ID)
Note

QC 20180518

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-05-18Bibliographically approved
Razzoli, E., Matt, C. E., Sassa, Y., Månsson, M., Tjernberg, O., Drachuck, G., . . . Shi, M. (2017). Rotation symmetry breaking in La2-xSrxCuO4 revealed by angle-resolved photoemission spectroscopy. Physical Review B, 95(22), Article ID 224504.
Open this publication in new window or tab >>Rotation symmetry breaking in La2-xSrxCuO4 revealed by angle-resolved photoemission spectroscopy
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2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 22, article id 224504Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-210475 (URN)10.1103/PhysRevB.95.224504 (DOI)000402799700005 ()
Funder
Swedish Research Council, 2016-06955
Note

QC 20170705

Available from: 2017-07-05 Created: 2017-07-05 Last updated: 2017-11-29Bibliographically approved
Wojek, B. M., Hårdensson Berntsen, M., Jonsson, V., Szczerbakow, A., Dziawa, P., Kowalski, B. J., . . . Tjernberg, O. (2015). Direct observation and temperature control of the surface Dirac gap in a topological crystalline insulator. Nature Communications, 6, Article ID 8463.
Open this publication in new window or tab >>Direct observation and temperature control of the surface Dirac gap in a topological crystalline insulator
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2015 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 6, article id 8463Article in journal (Refereed) Published
Abstract [en]

Since the advent of topological insulators hosting Dirac surface states, efforts have been made to gap these states in a controllable way. A new route to accomplish this was opened up by the discovery of topological crystalline insulators where the topological states are protected by crystal symmetries and thus prone to gap formation by structural changes of the lattice. Here we show a temperature-driven gap opening in Dirac surface states within the topological crystalline insulator phase in (Pb,Sn) Se. By using angle-resolved photoelectron spectroscopy, the gap formation and mass acquisition is studied as a function of composition and temperature. The resulting observations lead to the addition of a temperature-and composition-dependent boundary between massless and massive Dirac states in the topological phase diagram for (Pb,Sn) Se (001). Overall, our results experimentally establish the possibility to tune between massless and massive topological states on the surface of a topological system.

Place, publisher, year, edition, pages
Nature Publishing Group, 2015
Keywords
Phase-Transition, Pb1-Xsnxse, Semiconductors, System, SNTE
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-179283 (URN)10.1038/ncomms9463 (DOI)000364925900002 ()26458506 (PubMedID)2-s2.0-84944104336 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council
Note

QC 20151215

QC 20151216

Available from: 2015-12-15 Created: 2015-12-14 Last updated: 2017-12-01Bibliographically approved
Matt, C. E., Fatuzzo, C. G., Sassa, Y., Mansson, M., Fatale, S., Bitetta, V., . . . Chang, J. (2015). Electron scattering, charge order, and pseudogap physics in La1.6-xNd0.4SrxCuO4: An angle-resolved photoemission spectroscopy study. Physical Review B. Condensed Matter and Materials Physics, 92(13), Article ID 134524.
Open this publication in new window or tab >>Electron scattering, charge order, and pseudogap physics in La1.6-xNd0.4SrxCuO4: An angle-resolved photoemission spectroscopy study
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2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 13, article id 134524Article in journal (Refereed) Published
Abstract [en]

We report an angle-resolved photoemission study of the charge stripe ordered La1.6-xNd0.4SrxCuO4 (Nd-LSCO) system. A comparative and quantitative line-shape analysis is presented as the system evolves from the overdoped regime into the charge ordered phase. On the overdoped side (x = 0.20), a normal-state antinodal spectral gap opens upon cooling below 80 K. In this process, spectral weight is preserved but redistributed to larger energies. A correlation between this spectral gap and electron scattering is found. A different line shape is observed in the antinodal region of charge ordered Nd-LSCO x = 1/8. Significant low-energy spectral weight appears to be lost. These observations are discussed in terms of spectral-weight redistribution and gapping originating from charge stripe ordering.

Place, publisher, year, edition, pages
American Physical Society, 2015
Keywords
High-T-C, Temperature Cuprate Superconductors, Fermi-Surface Reconstruction, Copper-Oxide Superconductors, Stripe-Phase Order, Quantum Oscillations, Symmetry-Breaking, Energy Gaps, Underdoped Bi2sr2cacu2o8+Delta, Transition-Temperature
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-177053 (URN)10.1103/PhysRevB.92.134524 (DOI)000363518800002 ()2-s2.0-84946950112 (Scopus ID)
Funder
Wenner-Gren FoundationsSwedish Research Council, INCA-2014-6426
Note

QC 20151217

Available from: 2015-12-17 Created: 2015-11-13 Last updated: 2017-12-01Bibliographically approved
Sassa, Y., Mansson, M., Kobayashi, M., Gotberg, O., Strocov, V. N., Schmitt, T., . . . Batlogg, B. (2015). Probing two- and three-dimensional electrons in MgB2 with soft x-ray angle-resolved photoemission. Physical Review B. Condensed Matter and Materials Physics, 91(4), 045114
Open this publication in new window or tab >>Probing two- and three-dimensional electrons in MgB2 with soft x-ray angle-resolved photoemission
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2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 4, p. 045114-Article in journal (Refereed) Published
Abstract [en]

electronic band structure of MgB2 involves a unique combination of two-and three-dimensional (3D) electrons derived from the boron sigma and pi states, respectively. We have mapped out the sigma and pi bands over the complete Brillouin zone, including the full disconnected Fermi surface, using high-resolution soft x-ray angle-resolved photoelectron spectroscopy. The measured band structure, which is closely related to that of graphene, is in overall good agreement with the density functional theory-general gradient approximation (DFT-GGA), though differences in Fermi surface volume are seen. Surprisingly, the measured bands are wider than calculated, by similar to 8% for the s and similar to 10-15% for the p bands. This solves the long-standing challenge of establishing the full 3D electronic structure of the model compound MgB2, and it demonstrates the tendency of DFT-GGA to overestimate the band narrowing due to exchange correlations effects.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-160388 (URN)10.1103/PhysRevB.91.045114 (DOI)000348156100002 ()2-s2.0-84921038763 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20150226

Available from: 2015-02-26 Created: 2015-02-19 Last updated: 2017-12-04Bibliographically approved
Wojek, B. M., Dziawa, P., Kowalski, B. J., Szczerbakow, A., Black-Schaffer, A. M., Hårdensson Berntsen, M., . . . Tjernberg, O. (2014). Band inversion and the topological phase transition in (Pb,Sn)Se. Physical Review B. Condensed Matter and Materials Physics, 90(16), 161202
Open this publication in new window or tab >>Band inversion and the topological phase transition in (Pb,Sn)Se
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2014 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 16, p. 161202-Article in journal (Refereed) Published
Abstract [en]

The recent discovery of a topological phase transition in IV-VI narrow-gap semiconductors has revitalized the decades-old interest in the bulk band inversion occurring in these materials. Here we systematically study the (001) surface states of Pb1-xSnxSe mixed crystals by means of angle-resolved photoelectron spectroscopy in the parameter space 0 <= x <= 0.37 and 300 K >= T >= 9 K. Using the surface-state observations, we monitor directly the topological phase transition in this solid solution and gain valuable information on the evolution of the underlying fundamental band gap of the system. In contrast to common model expectations, the band-gap evolution appears to be nonlinear as a function of the studied parameters, resulting in the measuring of a discontinuous band-inversion process. This finding signifies that the anticipated gapless bulk state is in fact not a stable configuration and that the topological phase transition therefore exhibits features akin to a first-order transition.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-156989 (URN)10.1103/PhysRevB.90.161202 (DOI)000344024300001 ()2-s2.0-84908042676 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council
Note

QC 20150720

Available from: 2014-12-05 Created: 2014-12-04 Last updated: 2017-12-05Bibliographically approved
Månsson, M., Pra, K., Sassa, Y., Tobash, P. H., Bauer, E. D., Rusu, C., . . . Sugiyama, J. (2014). Magnetic order in the 2D Heavy-Fermion system CePt2In7 studied by μ+SR. In: 13TH INTERNATIONAL CONFERENCE ON MUON SPIN ROTATION, RELAXATION AND RESONANCE: . Paper presented at 13th International Conference on Muon Spin Rotation, Relaxation and Resonance, MuSR 2014; Grindelwald; Switzerland; 1 June 2014 through 6 June 2014 (pp. 012028). , 551(1), Article ID 012028.
Open this publication in new window or tab >>Magnetic order in the 2D Heavy-Fermion system CePt2In7 studied by μ+SR
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2014 (English)In: 13TH INTERNATIONAL CONFERENCE ON MUON SPIN ROTATION, RELAXATION AND RESONANCE, 2014, Vol. 551, no 1, p. 012028-, article id 012028Conference paper, Published paper (Refereed)
Abstract [en]

The low-temperature microscopic magnetic properties of the quasi-2D heavy- fermion compound, CePt2In7 are investigated by using a positive muon-spin rotation and relaxation (μ+SR) technique. Clear evidence for the formation of a commensurate antiferromagnetic order below TN 5.40 K is presented. The magnetic order parameter is shown to fit well to a modified BCS gap-energy function in a strong-coupling scenario.

Series
Journal of Physics Conference Series, ISSN 1742-6588 ; 551
Keywords
Charged particles, Spin dynamics, Spin-lattice relaxation, Temperature, Antiferromagnetic orderings, Energy functions, Heavy fermion compounds, Heavy-fermion systems, Low temperatures, Magnetic order parameter, Magnetic orders, Strong-coupling, Lanthanum compounds
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-168890 (URN)10.1088/1742-6596/551/1/012028 (DOI)000347715800028 ()2-s2.0-84919430250 (Scopus ID)
Conference
13th International Conference on Muon Spin Rotation, Relaxation and Resonance, MuSR 2014; Grindelwald; Switzerland; 1 June 2014 through 6 June 2014
Note

QC 20150609

Available from: 2015-06-09 Created: 2015-06-09 Last updated: 2015-06-09Bibliographically approved
Fatuzzo, C. G., Sassa, Y., Månsson, M., Pailhes, S., Lipscombe, O. J., Hayden, S. M., . . . Chang, J. (2014). Nodal Landau Fermi-liquid quasiparticles in overdoped La1.77Sr0.23CuO4. Physical Review B. Condensed Matter and Materials Physics, 89(20), 205104
Open this publication in new window or tab >>Nodal Landau Fermi-liquid quasiparticles in overdoped La1.77Sr0.23CuO4
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2014 (English)In: 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) Published
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.

Keywords
High-Temperature Superconductors, Electronic Specific-Heat, T-C Superconductor, Cuprate Superconductors, Quantum Oscillations, La2-Xsrxcuo4, Surface, Phase
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-146137 (URN)10.1103/PhysRevB.89.205104 (DOI)000335535600004 ()2-s2.0-84900519019 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20140610

Available from: 2014-06-10 Created: 2014-06-09 Last updated: 2017-12-05Bibliographically approved
Polley, C. M., Dziawa, P., Reszka, A., Szczerbakow, A., Minikayev, R., Domagala, J. Z., . . . Balasubramanian, T. (2014). Observation of topological crystalline insulator surface states on (111)-oriented Pb1-xSnxSe films. Physical Review B. Condensed Matter and Materials Physics, 89(7), 075317
Open this publication in new window or tab >>Observation of topological crystalline insulator surface states on (111)-oriented Pb1-xSnxSe films
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2014 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 7, p. 075317-Article in journal (Refereed) Published
Abstract [en]

We present angle-resolved photoemission spectroscopy measurements of the surface states on in-situ grown (111) oriented films of Pb1-xSnxSe, a three-dimensional topological crystalline insulator. We observe surface states with Dirac-like dispersion at (Gamma) over bar and (M) over bar in the surface Brillouin zone, supporting recent theoretical predictions for this family of materials. We study the parallel dispersion isotropy and Dirac-point binding energy of the surface states, and perform tight-binding calculations to support our findings. The relative simplicity of the growth technique is encouraging, and suggests a clear path for future investigations into the role of strain, vicinality, and alternative surface orientations in (Pb,Sn)Se solid solutions.

Keywords
Snte, Epitaxy, Phase
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-143704 (URN)10.1103/PhysRevB.89.075317 (DOI)000332421900004 ()2-s2.0-84897585096 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council
Note

QC 20150623

Available from: 2014-03-28 Created: 2014-03-27 Last updated: 2017-12-05Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-8669-6886

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