%0 Journal Article
%T Uhlmann Phase as a Topological Measure for One-Dimensional Fermion Systems
%A O. Viyuela
%A A. Rivas
%A M. A. Martin-Delgado
%J Physics
%D 2013
%I arXiv
%R 10.1103/PhysRevLett.112.130401
%X We introduce the Uhlmann geometric phase as a tool to characterize symmetry-protected topological phases in 1D fermion systems, such as topological insulators and superconductors. Since this phase is formulated for general mixed quantum states, it provides a way to extend topological properties to finite temperature situations. We illustrate these ideas with some paradigmatic models and find that there exists a critical temperature $T_c$ at which the Uhlmann phase goes discontinuously and abruptly to zero. This stands as a borderline between two different topological phases as a function of the temperature. Furthermore, at small temperatures we recover the usual notion of topological phase in fermion systems.
%U http://arxiv.org/abs/1309.1174v2