Fluctuation-Induced Torque on a Topological Insulator out of Thermal Equilibrium

Topological insulators with the time reversal symmetry broken exhibit strong magnetoelectric and magneto-optic effects. While these effects are well understood in or near equilibrium, nonequilibrium physics is richer yet less explored. We consider a topological insulator thin film, weakly coupled to...

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Bibliographic Details
Published in:Physical review letters 2019-08, Vol.123 (5)
Main Authors: Maghrebi, M. F., Gorshkov, A. V., Sau, J. D.
Format: Article
Language:English
Subjects:
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
Nonequilibrium fluctuations
Nonequilibrium Green's function
Physics
Topological insulators
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Summary:Topological insulators with the time reversal symmetry broken exhibit strong magnetoelectric and magneto-optic effects. While these effects are well understood in or near equilibrium, nonequilibrium physics is richer yet less explored. We consider a topological insulator thin film, weakly coupled to a ferromagnet, out of thermal equilibrium with a cold environment (quantum electrodynamics vacuum). We show that the heat flow to the environment is strongly circularly polarized, thus carrying away angular momentum and exerting a purely fluctuation-driven torque on the topological insulator film. Utilizing the Keldysh framework, we investigate the universal nonequilibrium response of the TI to the temperature difference with the environment. Lastly, we argue that experimental observation of this effect is within reach.
ISSN:0031-9007
1079-7114