Berlin 2024 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 74: Topological Insulators
TT 74.5: Talk
Thursday, March 21, 2024, 16:00–16:15, H 3005
Finite Size Effects in Magnetic Topological Insulators — •Joe Winter1,2, Bernd Braunecker2, and Ashley Cook1 — 1MPI PKS 38 Nöthnitzer Straße 01187 Dresden German — 2School of Physics and Astronomy, North Haugh, St Andrews KY16 9SS
The antiferromagnetic topological insulator phase is a foundational realization of three- dimensional topological phases of matter with magnetic order. Experimental evidence of the axion insulator phase in MnBi2Te4 for thin-film samples, a quasi-(3-1)-dimensional (q(3-1)D) geometry, therefore motivates investigation of finite-size topo- logical (FST) phases derived from the axion insulator phase. Here, we show the AFM TI does realize finite-size topological phases for the q(3-1)D geometry, with open-boundary conditions and small system size in one direction. We first characterize the FST phase diagram in the q(3-1)D bulk using Wannier spectral flow. We also confirm the defining response signature of the underly- ing 3D AFM TI phase, due to the topologically non-trivial magnetoelectric polarizability, persists in this geometry but only for the topologically non-trivial finite-size topological regions. We then open boundary conditions in a second direction to confirm the additional bulk-boundary corre- spondence of the finite-size topological phases, finding q(3-2)D topologically-protected, gapless edge modes. The co-existence of the q(3-2)D topologically non-trivial edge states with a topological response associated with the 3D bulk topological invariant, the magnetoelectric polarizability, further demonstrates that finite-size topology is a generic feature of topological phases and very relevant experimentally.
Keywords: Magnetic Topological Insulator; Finite size effects; Axion Insulator