Seminari del Dipartimento
Fisica Matematica (De)localization in topological insulators: a Wannier-function approach Domenico Monaco 02-05-2017 - 14:30 AULA 311 (SEMINARI) Largo San L. Murialdo,1
In this talk I will describe how Wannier functions (WFs) provide a powerful tool to investigate localization and transport properties of 2D and 3D gapped periodic quantum systems, including Chern insulators, quantum Hall systems, and time-reversal symmetric (TRS) topological insulators. In the first part of the talk, I will present a "localization dichotomy" for Chern and quantum Hall insulators, stating that either there exist exponentially localized WFs (in which case the Hall conductivity vanishes), or any system of WFs yields a divergent second moment of the position operator; no intermediate regimes are allowed. The second part of the talk will instead be devoted to TRS topological insulators: I will discuss how their Z_2 invariants arise as topological obstructions to the existence of localized and time-reversal symmetric WFs, and how to construct the latter in the unobstructed case. |