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Berlin 2018 – scientific programme

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MA: Fachverband Magnetismus

MA 29: Topological Insulators I (joint session TT/MA)

MA 29.4: Talk

Wednesday, March 14, 2018, 12:30–12:45, A 053

Topological invariants for Floquet-Bloch systems with chiral, time-reversal, or particle-hole symmetry — •Bastian Höckendorf, Andreas Alvermann, and Holger Fehske — Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, Greifswald, Germany

We introduce Z2-valued bulk invariants for symmetry-protected topological phases in 2+1 dimensional driven quantum systems. These invariants adapt the W3-invariant, expressed as a sum over degeneracy points of the propagator, to the respective symmetry class of the Floquet-Bloch Hamiltonian. The bulk-boundary correspondence that holds for each invariant relates a non-zero value of the bulk invariant to the existence of symmetry-protected topological boundary states. To demonstrate this correspondence we apply our invariants to a chiral Harper, time-reversal Kane-Mele, and particle-hole symmetric graphene model with periodic driving, where they successfully predict the appearance of boundary states that exist despite the trivial topological character of the Floquet bands. Especially for particle-hole symmetry, combination of the W3 and the Z2-invariants allows us to distinguish between weak and strong topological phases.
B. Höckendorf, A. Alvermann, and H. Fehske, J. Phys. A 50, 295301 (2017).
B. Höckendorf, A. Alvermann, and H. Fehske, preprint, arXiv:1708.07420 (2017).

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