Doctoral Thesis Defence
Talk by Johan Ekström
Topology in condensed matter physics is a field that has exploded in the last two decades. With the realization of its importance, some previously unexplained observations are now understood. As time has passed, many new topological phases of matter have been discovered, and topological materials have been shown to be fairly common in nature. Topological materials have further been shown to have properties that may be extremely useful for new technologies, such as spintronics and fault-tolerant quantum computation. The field is, however, still evolving, and many properties of these materials are still unknown. We have studied how some of these types of materials react to applied external fields and the theories that can explain these observations.
We first investigate the transport properties of systems hosting coupled Majorana bound states, where, moreover, the overlap between the Majorana bound states, multiple terminals, and charging energy are considered. The transport properties are studied in both the sequential tunneling regime and the Coulomb blockaded regime, and we show that multi-terminal measurements can be useful for the characterization of the properties of MBSs with finite overlaps and charging energy.
Thereafter we investigate the Kerr effect in tilted nodal loop semimetals. As light is reflected on the surface of a material, its polarization might change. This is the Kerr effect. We study this both for a thin film and a bulk material hosting a nodal loop. Our results show, similar to other topological materials, that large Kerr rotations should be observed for this type of material.
Finally, we study two-dimensional electronic systems in the hydrodynamic regime. First, we derive the electronic Navier-Stokes equation and show how it is modified by the presence of the Berry curvature. Thereafter we study electron transport governed by the derived Navier-Stokes equation for two different setups. We find that the Berry curvature affects the Poiseuille flow as well as flow in a half-plane geometry and propose how the effects can be measured in experiments.
Dissertation defence committee:
Chairman: Assistant Professor, Dr Etienne Fodor, Université du Luxembourg
Professor, Dr. Thomas Schmidt, dissertation supervisor, Université du Luxembourg
Professor, Dr. Susanne Siebentritt, Université du Luxembourg
Professor, Dr. Fabian Hassler, RWTH Aachen University
Professor, Dr. Alexander Holleitner, Technische Universität München