October 31, 2023

Speaker: Meng Cheng  (Yale)

Title: A defective look at quantum phases of matter

Abstract: I will discuss recent developments in the classification and characterization of phases of matter in quantum many-body systems, through the lens of topological defects of global symmetry. In the first part, I will review how gapped phases with spatial symmetries can be understood using networks of background defects, and apply the construction to derive topological boundary states of (4+1)d "beyond-cohomology" SPT phases. The second part will discuss topological phases in condensed matter systems with quenched disorder. Viewing disordered phases as ensembles of defects, I will describe a classification scheme of disordered topological phases with exact and average symmetries.