Average symmetry-protected topological phases: the decohered, the disordered, and the intrinsic

Symmetry-protected topological (SPT) phases have attracted significant attention in the field of condensed matter physics due to their remarkable properties, such as the presence of protected edge or surface modes. Although substantial progress has been made in understanding these phases in ideal, isolated systems at zero temperature, their behavior under non-ideal conditions involving measurement, decoherence, or disorder presents a challenging area of study. In this talk, a  new concept known as "averaged symmetry-protected topological phases" will be introduced. These phases exist within mixed ensembles where individual states break part of the protecting symmetry, but the symmetry is restored upon ensemble averaging. We will explore the physical properties and classification schemes for these unique phases. Additionally, we will introduce the notion of a "strange correlator" as a theoretical and numerical tool for detecting these phases.

Faculty Hosts: Eun-Ah Kim and Debanjan Chowdhury