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Spin-polarized edge currents and Majorana fermions in one- and two-dimensional topological superconductors
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
KTH Royal Inst Technol, Ctr Quantum Mat, Nordita, S-10691 Stockholm, Sweden.;Stockholm Univ, S-10691 Stockholm, Sweden..
KTH Royal Inst Technol, Ctr Quantum Mat, Nordita, S-10691 Stockholm, Sweden.;Stockholm Univ, S-10691 Stockholm, Sweden.;Los Alamos Natl Lab, Inst Mat Sci, Los Alamos, NM 87545 USA..
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 21, 214501Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

We investigate the persistent currents, spin-polarized local density of states, and spectral functions of topological superconductors constructed by placing ferromagnetic impurities on top of an s-wave superconductor with Rashba spin-orbit interaction. We solve self-consistently for the superconducting order parameter and investigate both two-dimensional blocks and one-dimensional wires of ferromagnetic impurities, with the magnetic moments pointing both perpendicular and parallel to the surface. We find that the topologically protected edge states of ferromagnetic blocks give rise to spin-polarized edge currents, but that the total persistent current flows in opposite direction to what is expected from the dispersion relation of the edge states. We also show that the Majorana fermions at the end points of one-dimensional wires are spin polarized, which can be directly related to the spin polarization of the edge currents of two-dimensional blocks. Connections are also made to the physics of the Yu-Shiba-Rusinov states for zero-dimensional impurities.

Place, publisher, year, edition, pages
2015. Vol. 92, no 21, 214501
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-270955DOI: 10.1103/PhysRevB.92.214501ISI: 000365773700002OAI: oai:DiVA.org:uu-270955DiVA: diva2:890868
Funder
Swedish Research CouncilGöran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologySwedish Foundation for Strategic Research EU, European Research Council, DM-321031
Available from: 2016-01-05 Created: 2016-01-05 Last updated: 2017-12-01Bibliographically approved
In thesis
1. Topological band theory and Majorana fermions: With focus on self-consistent lattice models
Open this publication in new window or tab >>Topological band theory and Majorana fermions: With focus on self-consistent lattice models
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One of the most central concepts in condensed matter physics is the electronic band structure. Although band theory was established more than 80 years ago, recent developments have led to new insights that are formulated in the framework of topological band theory. In this thesis a subset of topological band theory is presented, with particular focus on topological supercon- ductors and accompanying Majorana fermions. While simple models are used to introduce basic concepts, a physically more realistic model is also studied intensely in the papers. Through self- consistent tight-binding calculations it is confirmed that Majorana fermions appear in vortex cores and at wire end points when the superconductor is in the topologically non-trivial phase. Many other properties such as the topological invariant, experimental signatures in the local density of states and spectral function, unconventional and odd-frequency pairing, the precense of spin-polarized currents and spin-polarization of the Majorana fermions, and a local π-phase shift in the order parameter at magnetic impurities are also investigated. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 144 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1441
Keyword
Topology, Majorana, superconductivity, material physics, numerical calculations, tight-binding, mean-field
National Category
Condensed Matter Physics Physical Sciences
Identifiers
urn:nbn:se:uu:diva-305212 (URN)978-91-554-9728-6 (ISBN)
Public defence
2016-12-09, Häggsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2016-11-15 Created: 2016-10-12 Last updated: 2016-11-23

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Björnson, KristoferBlack-Schaffer, Annica M.

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