Regensburg 2025 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 61: THz and MIR physics in semiconductors

HL 61.3: Vortrag

Freitag, 21. März 2025, 11:15–11:30, H14

Diminishing topological Faraday effect in thin layer samples — Christian Berger, Florian Bayer, Laurens W. Molenkamp, and •Tobias Kießling — Physikalisches Institut, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany

A striking feature of three-dimensional topological insulators (TIs) is the theoretically expected topological magnetoelectric (TME) effect, which gives rise to additional terms in Maxwell's laws of electromagnetism with an universal quantized coefficient proportional to half-integer multiples of the fine-structure constant. In an ideal scenario one therefore expects also quantized contributions in the magnetooptical response of TIs.

We review this premise by taking into account the trivial dielectric background of the TI bulk and potential host substrates, and the often present contribution of itinerant bulk carriers. We show (i) that one obtains a nonuniversal magnetooptical response whenever there is impedance mismatch between different layers and (ii) that the detectable signals due to the TME rapidly approach vanishingly small values as the impedance mismatch is detuned from zero.

Keywords: Topological Insulators; Magneto-electric effect; Faraday effect