Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 42: Transport: Topological Insulators 3 (jointly with DS, HL, MA, O)

TT 42.6: Vortrag

Dienstag, 17. März 2015, 15:15–15:30, H 0110

Cherenkov effect in topological insulators — •Sergey Smirnov — Institute for theoretical physics, Regensburg University, 93040 Regensburg, Germany

The Cherenkov radiation discovered experimentally by Cherenkov in optics of transparent media and theoretically explained later by Tamm and Frank reappears in solids where particles move faster than sound and, as a result, excite lattice vibrations or phonons. In both cases the photons or phonons are distributed within a forward cone centered around the momentum of the particle producing the Cherenkov light or sound.

Here we demonstrate that at high energies helical particles on surfaces of topological insulators excite anomalous Cherenkov sound outside the forward cone when the anisotropy of the surface states exceeds a critical value. The sound features many outstanding properties. In particular, at strong anisotropy it localizes into a few forward and backward beams propagating along specific directions [1].

At low energies we predict that an in-plane magnetic field applied to a surface of a topological insulator will asymmetrically reverse the Cherenkov sound. This asymmetric Cherenkov acoustic reverse may be of practical relevance in design of low energy electronic devices such as acoustic ratchets or, in general, in low power design of electronic circuits with an external control of the Cherenkov dissipation [2].

[1] S. Smirnov, Phys. Rev. B 88, 205301 (2013).

[2] S. Smirnov, Phys. Rev. B 90, 125305 (2014).