Quantized Faraday and Kerr rotation and axion electrodynamics of a 3D topological insulator

Topological insulators have been proposed to be best characterized as bulk magnetoelectric materials that show response functions quantized in terms of fundamental physical constants. Here, we lower the chemical potential of three-dimensional (3D) Bi₂Se₃ films to ~3O meV above the Dirac point and pr...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2016-12, Vol.354 (6316), p.1124-1127
Main Authors: Wu, Liang, Salehi, M., Koirala, N., Moon, J., Oh, S., Armitage, N. P.
Format: Article
Language:English
Subjects:
Coupling
Electrodynamics
Electromagnetism
Insulators
Invariants
Magnetic properties
Materials science
Thin films
Time domain
Topology
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Summary:Topological insulators have been proposed to be best characterized as bulk magnetoelectric materials that show response functions quantized in terms of fundamental physical constants. Here, we lower the chemical potential of three-dimensional (3D) Bi₂Se₃ films to ~3O meV above the Dirac point and probe their low-energy electrodynamic response in the presence of magnetic fields with high-precision time-domain terahertz polarimetry. For fields higher than 5 tesla, we observed quantized Faraday and Kerr rotations, whereas the dc transport is still semiclassical. A nontrivial Berry's phase offset to these values gives evidence for axion electrodynamics and the topological magnetoelectric effect. The time structure used in these measurements allows a direct measure of the fine-structure constant based on a topological invariant of a solid-state system.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.aaf5541