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Disputation Kevin Alan Madsen

18.02.2022 | 15:30
Thema der Dissertation:
Linearly dispersing electrons: Effects of magnetic coupling and disorder
Abstract: In this thesis we study systems with linearly dispersing electrons and the effects disorder and a magnetic coupling can have on them. We focus on three examples: First we study the effects of potential disorder on the density of states at the nodal points in two-dimensional graphene and in three-dimensional Weyl semimetals. We obtain high-precision numerical data for the density of states of single nodal points and compare it to analytical perturbation theory calculations. At weak disorder strength, our results for the Weyl semimetal show a semimetallic phase with (to numerical accuracy) zero density of states at the nodal point. At stronger disorder strength, we find a finite density of states at the nodal point, in agreement with theoretical expectations. Second we study the effects of a magnetic coupling on the one-dimensional chiral edge states of a two-dimensional topological insulator incorporated in a two-arm interferometer geometry and we find that due to the coupling to a magnetic insulator and interference effects a time-independent bias voltage can give rise to time-dependent currents. Additionally, Aharonov-Bohm oscillations due to a flux through the device are strongly suppressed at small applied bias voltages. The third and last example is a layered heterostructure consisting of a finite-width slab of a magnetic Weyl semimetal placed on top of a superconductor. The asymmetry of the heterostructure caused by the superconductor only being coupled to one of the two surfaces of the slab leads to an equilibrium current that flows parallel to the interface and we are able to show that it is carried mostly by the Fermi-arc surface states of the Weyl semimetal.

Zeit & Ort

18.02.2022 | 15:30

Hörsaal A (1.3.14)
Fachbereich Physik, Arnimallee 14, 14195 Berlin

*Die Teilnahme ist nur unter der strikten Einhaltung der 3G Regelungen möglich*