TRR 360 Seminar:

Making sense of band topology in open quantum systems

Frank Schindler

Making sense of band topology in open quantum systems

Dr. Frank Schindler

Imperial College London, United Kingdom

There has been a great deal of work in generalising the notion of band topology to the non-equilibrium setting. Much of this effort has focused on non-Hermitian Hamiltonians that are thought of as describing quantum systems with loss and gain. In the first part of my talk, I will pedagogically explain one of the central results of this field — the winding number and associated skin effect. I will then argue, however, that the non-Hermitian framework is fundamentally inadequate to properly describe quantum many-body systems — even non-interacting ones — calling into question the physical relevance of non-Hermitian topological invariants. I will end my talk by working out to what extent such invariants, in particular the winding number, can be saved in the more general Lindblad description of open quantum systems.