Mainz 2017 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 52: Quantum Gases: Fermions II

Q 52.5: Vortrag

Donnerstag, 9. März 2017, 15:30–15:45, P 204

Topological order in finite-temperature Gaussian fermionic systems — •Lukas Wawer, Dominik Linzner, and Michael Fleischhauer — Fachbereich Physik und Forschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Deutschland

Since their discovery, topological states of matter have been praised for their fascinating and potentially useful properties as protected edge states or anyonic excitations. However, these features seem to vanish at finite temperature. Exploiting the equivalence of Zak (or Berry) phase and polarization we can classify topological order in finite-temperature systems by means of the many body polarization [1]. We show that topological order defined in this way survives at any finite temperature in Gaussian fermionic systems. On the one hand we consider a 1D model for symmetry protected topological order (Su-Schrieffer-Heeger model) and find that there is a quantized winding of the polarization for closed paths in parameter space. On the other hand we study a 2D model (Hofstadter-Hubbard model) with intrinsic topology and show that there is an integer change of polarization at any finite temperature if we go through the Brillouin zone. This change of polarization can be identified as the counterpart of the Chern number in closed 2D models. [1] D. Linzner, L. Wawer, F. Grusdt, and M. Fleischhauer, Phys. Rev. B 94, 201105(R) (2016)