Theoretical Physics Seminar: Oindrila Deb (Basel)

Title : Exploring Topological systems : from Topological Insulators to Majorana Bound States

Abstract :Topological systems have fundamentally enriched our understanding of quantum phases of matter. One of the hallmarks of such phases is the presence of the gapless modes at the boundary of the system whereas the bulk modes are gapped. Topological insulators (TI) and topological superconductors (TSC) are two important examples of such systems. In my talk, I will discuss the exotic physics happening at the junctions of such materials. I will begin with a discussion on the transport across the junction between two TI surfaces. I will show that the application of a potential along the junction can give rise to localized edge states whose velocity and spin orientation depend on the applied potential. Next, I will discuss the transport in a Y-shaped junction of three TSCs connected to normal metal leads. The number of Majorana bound states (MBS) that appear at such junctions or equivalently the number of conductance peaks depends on the relative phases of the pairing potentials in the superconductors. Finally, I will discuss the physics of magnetic impurities sitting on a superconductor (SC). It is well-known that a chain of magnetic impurities on a two-dimensional SC with strong spin-orbit coupling, hosts MBS at the ends of the chain. As a first step towards understanding the complicated physics of the magnetic chain, we have worked with a dimer of magnetic impurities. I will explain how the magnetic ground state of the dimer changes as a function of the inter-impurity distance.