Asymmetric Cherenkov acoustic reverse in topological insulators

TL;DR

This paper explores how applying an in-plane magnetic field to three-dimensional topological insulators can control Cherenkov sound, enabling a switch from forward to backward emission, with potential applications in low-power electronic devices.

Contribution

It introduces a novel magnetic field-controlled reversal of Cherenkov acoustic radiation in topological insulators, revealing a new way to manipulate sound emission direction.

Findings

Magnetic field suppresses forward Cherenkov sound at a critical value.

Above the critical field, Cherenkov sound becomes purely backward.

Potential for magnetic control of acoustic dissipation in electronic devices.

Abstract

A general phenomenon of the Cherenkov radiation known in optics or acoustics of conventional materials is a formation of a forward cone of, respectively, photons or phonons emitted by a particle accelerated above the speed of light or sound in those materials. Here we suggest three-dimensional topological insulators as a unique platform to fundamentally explore and practically exploit the acoustic aspect of the Cherenkov effect. We demonstrate that applying an in-plane magnetic field to a surface of a three-dimensional topological insulator one may suppress the forward Cherenkov sound up to zero at a critical magnetic field. Above the critical field the Cherenkov sound acquires pure backward nature with the polar distribution differing from the forward one generated below the critical field. Potential applications of this asymmetric Cherenkov reverse are in design of low energy electronic devices such as acoustic ratchets or, in general, in low power design of electronic circuits with a magnetic field control of the direction and magnitude of the Cherenkov dissipation.