Regensburg 2025 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 4: Topological Insulators
TT 4.7: Vortrag
Montag, 17. März 2025, 11:00–11:15, H33
Finite size topology in magnetic topological insulators — •Joe Winter1,2, Michał Pacholski1, and Ashley Cook1 — 1MPI PKS, Dresden, Germany — 2University of St Andrews, St Andrews, Scotland
The antiferromagnetic topological insulator phase is a foundational realization of three-dimensional topological phases of matter with magnetic order. It is furthermore an example of an axion insulator and condensed matter platform for realizing exotic axion dynamics of high-energy physics. At systems sizes where the sample size is comparable with the correlation length of the topological surface states, it is expected for these states to hybridise. We however show the strength of this hybridisation is oscillatory with respect to system parameters and resonances occur where the surface states can reform. We then confirm the defining response signature of the underlying 3D AFM TI phase persists in this geometry, at these resonances. We then open boundary conditions in a second direction to confirm the additional bulk-boundary correspondence of the finite-size topological phases spectral flow, 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, confirms finite-size AFM topological phases occur. This further demonstrates that finite-size topology is a generic feature of topological phases and very relevant experimentally.
Keywords: Magnetic Topological Insulators; Axion; Thin Film; Bulk Boundary Correspondence; Helical Edge States