Cherenkov sound on a surface of a topological insulator

Abstract

Topological insulators are currently of considerable interest due to peculiar electronic properties originating from helical states on their surfaces. Here we demonstrate that the sound excited by helical particles on surfaces of topological insulators has several exotic properties fundamentally different from sound propagating in non-helical or even isotropic helical systems. Specifically, the sound may have strictly forward propagation absent for isotropic helical states. Its dependence on the anisotropy of the realistic surface-states is of distinguished behavior which may be used as an alternative experimental tool to measure the anisotropy strength. Fascinating from the fundamental point of view backward, or anomalous, Cherenkov sound is excited above the critical angle $\pi /2$ when the anisotropy exceeds a critical value. Strikingly, at strong anisotropy the sound localizes into a few forward and backward beams propagating along specific directions.

9 pages, 15 figures

References in corpus (8)

• Topological Insulators
• Topological insulators and superconductors
• Quantum Spin Hall Insulator State in HgTe Quantum Wells
• Model Hamiltonian for Topological Insulators
• Nonlocal edge state transport in the quantum spin Hall state
• Hexagonal Warping Effects in the Surface States of Topological Insulator Bi${}_2$Te${}_3$
• The Helical Liquid and the Edge of Quantum Spin Hall Systems
• Anomalous Cherenkov spin-orbit sound

Cited by in corpus (4)

• Reversed electromagnetic Vavilov-Čerenkov radiation in naturally existing magnetoelectric media
• Cherenkov radiation and emission of surface polaritons from charges moving paraxially outside a dielectric cylindrical waveguide
• Asymmetric Cherenkov acoustic reverse in topological insulators
• Orthogonal Cherenkov sound in spin-orbit coupled systems