28 September 2021

Seminar DMONS : Nico Leumer

"Analytical approaches to 1d topological superconductors of finite size"

Speaker : Nico Leumer (IPCMS-DMONS)

Place : Auditorium de l’IPCMS, en présentiel, probablement avec possibilité de suivre en ligne

Abstract : The experimental search for Majorana zero modes, which are exotic modes hosted only by so-called topological superconductors, is despite numerous challenges still an ongoing „hot“ topic. Rather ordinary ingredients, as for instance magnetic fields, s-wave superconductivity and spin-orbit coupling, can turn a „normal“ materiel into such a topological superconductor, as demonstrated for (1d) InAs nanowires [1-3] or carbon nanotubes [4]. Thus, Majorana zero modes (MZM) can be engineered under appropriate conditions. Apart from their exotic nature, MZMs can be also relevant for practical purposes and offer indeed a platform for fault tolerant quantum computation [5].
    Although the underlying mechanisms such as the topological classification of systems and also topological superconductors are well understood from a theoretical point of view, the undeniable experimental detection of MZM is still an open issue. In theory, systems are considered either as infinitely long or treated numerically. Alternatively, one refers to toy models.
    The archetypal toy model of (1d) topological superconductors is the Kitaev chain. Contrary to many other models, the outstanding feature of the Kitaev chain is its apparent simplicity and the opportunity to find exact analytical expression for its spectrum even in the case of open boundary conditions (opc) and finite size [6,7]. In my talk, I will show that opc and finite size are essential for proper theoretical predictions. Further, the proper physical understanding of the Kitaev chain allows directly the analytical treatment of realistic models (finite size and opc) as I will demonstrate in case of the Rashba-nanowires [8]. In order to be appreciated also by non-experts of Majorana fermions in condensed matter, I first introduce the main aspects of this research field and try to sketch important relations within the topic.

[1] Y. Oreg, G. Refael and F. von Oppen, PRL 105, 177002 (2010)
[2] R. M. Lutchyn, J. D. Sau, and S. Das Sarma, PRL 105, 077001 (2010)
[3] J. Alicea, Rep. Prog. Phys. 75, 076501 (2012)
[4] L. Milz, W. Izumida, M. Grifoni and M. Marganska, PRB 100, 155417 (2019)
[5] A. Y. Kitaev, Phys. Usp. 44, 131 (2001)
[6] N. Leumer, M. Marganska, B. Muralidharan, and M. Grifoni, J. Phys.: Condens. Matter 32, 445502 (2020)
[7] N. Leumer, M. Grifoni, B. Muralidharan, and M. Marganska, Phys. Rev. B 103, 165432 (2021)
[8] H. Schmid, MA thesis, University of Regensburg (2020)

The connection links will be as follows :

Zoom access   https://zoom.us/j/7296665252?pwd=YzN4WjlsK1l0T3VmUkNnS0pjUUVhUT09

Meeting ID : 729 666 5252

Secret Code : 123456789

28 September 2021, 11h0012h00
Auditorium de l'IPCMS
23 rue du Loess
67034 Strasbourg

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