Andrej Mesaros
Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides

Andrej Mesaros

“Topological defects in spin-orbit coupling”

Observing defects in a system has been a useful tool for identifying the locally ordered state. Recently, topological defects have become an essential tool for topological systems, which range from electrons to macroscopic metamaterials, because they can probe or even create the non-local order. I will briefly overview the ideas of topological defects and states, and then introduce electronic topological insulators and superconductors, with the important role of Spin-Orbit Interaction (SOI).

I will discuss our two recent theoretical results. First, experiments on graphene haven’t been able to enhance the type of SOI which creates a bulk topological insulator state and its desired robust edge states. Our prediction is that domain-wall defects in the experimentally-induced type of SOI (“valley-Zeeman” type), already carry the desired robust one-dimensional states.

I will also discuss microscopy experiments on superconducting monolayer of lead(Pb) grown over islands of cobalt atoms, which shows island edge modes, but also unexpected point-like electronic excitations on island centers. We theoretically find that a vortex defect in Rashba-type SOI fully explains puzzling real-space and spectral features of this experiment. The vortex excitation is interpreted as the highly-sought point-like Majorana bound state.