Theory Seminar: Exceptional Topology of Non-Hermitian Systems

Emil Bergholtz (Stockholm University)
Non-Hermitian Hamiltonians have become an important asset for the effective description of various physical systems that are subject to dissipation.

Emil Bergholtz (Stockholm University)
Herbert-Walther Lecture Hall G0.25
Wed, 17. January 2020, 11:30 am

Abstract:

Non-Hermitian Hamiltonians have become an important asset for the effective description of various physical systems that are subject to dissipation. Using simple examples, I will discuss several new topological phenomena and relate them to uniquely non-Hermitian concept of exceptional degeneracies at which both eigenvalues and eigenvectors coalesce. In particular, this includes the occurrence of Fermi arcs in two dimensions, three-dimensional knotted metals featuring open Fermi-Seifert surfaces, new symmetry protected phases and a bulk-boundary correspondence strikingly distinct from that known from the Hermitian realm. Along the way I will give examples on how these phenomena can be realised in settings ranging from optical setups with gain and loss, electric circuits, and mechanical systems, to quantum many-body systems such as electronic transport settings at material junctions. Reference: arXiv:1912.10048