Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 76: Topology: Other Topics
TT 76.1: Vortrag
Mittwoch, 14. März 2018, 17:00–17:15, A 053
Robustness and quantum phase transitions of the perturbed 3D toric code — •David A. Reiss1,2 and Kai P. Schmidt2 — 1Dahlem Center for Complex Materials and Physics Department, Free University Berlin — 2Chair for Theoretical Physics 1, University of Erlangen-Nürnberg
Topological quantum order in 3D represents quantum phases with exotic excitations which are spatially extended and have anyonic statistics different from bosons and fermions. This talk discusses the robustness against quantum fluctuations and the quantum phase transitions of a paradigmatic example, the 3D toric code in a uniform magnetic field. First, the qualitative dynamics of its quasiparticles according to perturbation theory is reviewed: the point excitations are mobile, while the single constituents of spatially extended excitations stay spatially localized to all orders of perturbation theory in a translationally invariant system without disorder. This is similar to excitations in so-called fracton phases, which might be employed as thermally stable topologically-protected quantum memories in contrast to the 3D toric code. Second, a variational ansatz and exact duality relations of special magnetic field cases of the toric code to other models are employed to determine the zero-temperature phase diagram. The main results are that (1) for the breakdown of 3D topological quantum order, the exotic mutual statistics of the point excitations and the spatially extended excitations is not relevant compared to their deconfinement and confinement, respectively, and that (2) the perturbed 3D toric code is robust and features a rich phase diagram.