This is part of a virtual seminar series in theoretical condensed matter and atomic physics, with the aim to connect researchers working at different Nordic universities.
Abstract: One standard assumption for classifying topological phases of matter is that the system has an (at least partial) energy gap. More precisely, the corresponding topological invariants become generically ill-defined when the system becomes gapless, i.e. at critical points. Nevertheless, it was observed that certain hallmarks of topological phases, in particular the presence of robust edge modes, survive at criticality. In this talk, we discuss two distinct ways of how to generalize topological invariants to systems without an energy gap, as well as their properties. We will also introduce a relation between critical hermitian and gapped non-hermitian phases, using the example of one-dimensional systems with chiral symmetry.
Zoom-link: https://nordita.org/zoom/nvcms
Condensed Matter Physics Seminar