The Uhlmann connection in fermionic systems undergoing phase transitions
Abstract
We study the behaviour of the Uhlmann connection in systems of fermions undergoing phase transitions. In particular, we analyse some of the paradigmatic cases of topological insulators and superconductors in dimension one, as well as the BCS theory of superconductivity in three dimensions. We show that the Uhlmann connection signals phase transitions in which the eigenbasis of the state of the system changes. Moreover, using the established fidelity approach and the study of the edge states, we show the absence of thermally driven phase transitions in the case of topological insulators and superconductors. We clarify what is the relevant parameter space associated with the Uhlmann connection so that it signals the existence of order in mixed states.
Cite
@article{arxiv.1702.07289,
title = {The Uhlmann connection in fermionic systems undergoing phase transitions},
author = {Bruno Mera and Chrysoula Vlachou and Nikola Paunković and Vítor R. Vieira},
journal= {arXiv preprint arXiv:1702.07289},
year = {2017}
}
Comments
14 pages (including Supplemental Material); Updated with new results; Accepted for publication in Physical Review Letters