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Miguel A. Martin-Delgado

Universidad Complutense de Madrid, Spain

Symmetry-Protected Topological Orders at Finite Temperature

23 Feb 2016 14:00
PGl Lecture Hall, Bld. 04.8, 2. floor, Room 365

Abstract: We construct a topological invariant that classifies density matrices of symmetry protected topological orders in two‐dimensional fermionic systems. As it is constructed out of the previously introduced Uhlmann phase, we refer to it as the topological Uhlmann number nU.

With it, we study thermal topological phases in several two‐dimensional models of topological insulators and superconductors, computing phase diagrams where the temperature T is on an equal footing with the coupling constants in the Hamiltonian. Moreover, we find novel thermal‐topological transitions between two non‐trivial phases in a model with high Chern numbers. At small temperature we recover the standard topological phases as the Uhlmann number approaches to the Chern number.

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