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Topological quantum bound states: Shiba, Majorana, and parafermions bound states

English title Topological quantum bound states: Shiba, Majorana, and parafermions bound states
Applicant Klinovaja Jelena
Number 163295
Funding scheme Project funding (Div. I-III)
Research institution Departement Physik Universität Basel
Institution of higher education University of Basel - BS
Main discipline Theoretical Physics
Start/End 01.09.2016 - 31.03.2021
Approved amount 502'711.00
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All Disciplines (2)

Discipline
Theoretical Physics
Condensed Matter Physics

Keywords (8)

Shiba bound states; topological superconductivity; topological quantum computing; topological insulators; magnetic impurities; spin filters; spin-based quantum computing; Majorana and parafermion bound states

Lay Summary (German)

Lead
Gebundene topologische Quanten-Zustände: Gebundene Shiba-, Majorana- und parafermionische Zustände
Lay summary

Trotz seiner relativ jungen Geschichte hat das Feld der topologischen Quanteneffekte das Potential, eine wesentliche Rolle in zukünftigen Technologien zu spielen. Zu Beginn wurden in diesem Feld rein theoretische Arbeiten zu topologisch geschützten Schemata für Quantencomputer veröffentlicht. Innerhalb kürzester Zeit wurden jedoch bahnbrechende Experimente, welche Anzeichen für toplogische Isolatoren, sowie gebundene Majorana-Zustände zeigten, durchgeführt. Diese wegweisenden Experimente geben Anlass zur Hoffnung, dass, obwohl schwer zugänglich, topologische Effekte und deren einzigartige Stabilität gegenüber lokalen Störungen tatsächlich in der Natur vorkommen.

Das Hauptziel dieses Proposals ist es, einen wesentlichen Beitrag zum Fortschritt des schnell wachsenden Gebietes der topologischen Quanteneffekte zu leisten, insbesondere mit einem engen Bezug zu den aktuellen Experimenten. Motiviert durch jüngste Experimente in Princeton und unserem Institut, welche die ersten Hinweise auf gebundene Majorana-Zustände lieferten, liegt ein Augenmerk unseres Proposals auf atomaren magnetischen Ketten auf supraleitenden Oberflächen. Dennoch sind sich Experten weltweit über die Interpretation der Resultate nicht einig. Dies ist darauf zurückzuführen, dass in einer ersten theoretischen Analyse viele Effekte vernachlässigt wurden. Eine systematische Analyse mithilfe von analytischen, sowie numerischen Methoden ist für die wachsende Anzahl von Aktivitäten in diesem Feld unabdingbar. Darüber hinaus verfolgen wir die Strategie, nicht ausschliesslich schon existierende Systeme zu charakterisieren, sondern weiterhin nach experimentell relevanten, d.h. insbesondere realisierbaren, Systemen mit topologischen Eigenschaften zu suchen. 

Direct link to Lay Summary Last update: 25.07.2016

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Abstract

The present proposal focuses on topological quantum effects in condensed matter physics. Topological quantum effects is a relatively young field, however, it has the potential to become an essential part of future technology. The field began with purely theoretical proposals on topologically protected quantum computation schemes, however, in a very short time, first seminal experiments demonstrating signatures of topological insulators and Majorana bound states were carried out. These pioneering experiments give us hope that indeed topological effects and their unique stability to local perturbations exist in Nature even if it is not so straightforward to access them. The main goal of this proposal is to substantially contribute to the current progress of the emerging field of topological quantum effects with a strong link to experimental activity carried out in this area. One of the focus of our proposal lies on atomic magnetic chains on superconducting surfaces. Here, we are motivated by recent experiments in Princeton and at my home institution that observed the first signature of Majorana bound states. However, their interpretation is still under intense debate by leading experts worldwide as many effects were not taken into account in the first theoretical analyses. The systematic analytical and numerical studies are of great importance for this growing field of activities. Moreover, the strategy we pursue is not to focus on characterization of already existing systems but also to continue the search for the experimentally relevant systems with topological properties. By combining well-known ingredients, such as spin orbit interaction (intrinsic and synthetic), superconductivity, and electron-electron interactions, we plan to identify novel setups which can host topological excitations, in particular of non-Abelian character such as Ising or Fibonacci anyons. In particular, we plan to work on the following topics:2.A Single magnetic impurities on superconducting surfaces. Suppression of the local superconducting pairing amplitude, magnetic configuration of two spin impurities, \pi junction, Shiba bound states, Andreev bound states.2.B Chains of magnetic impurities: generation and manipulation of Majorana bound states. RKKY systems and Majorana bound states, interpretation of recent experiments, proximity-induced superconductivity in atomic chains, localization lengths, local change of the topological criterion.2.C Edge states of two-dimensional topological insulators: Majorana bound states and parafermions. Local magnetic doping, spin filtering effects, fast spin-switches manipulated by electric fields, electron-electron interactions.
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