Absorption of surface acoustic waves by topological insulator thin films

Journal Article · Mon Aug 11 00:00:00 EDT 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4893002· OSTI ID:22318022

Li, L. L., E-mail: [e-mail] ^[1]; Xu, W., E-mail: [e-mail] ^[1]; Department of Physics, Yunnan University, Kunming 650091 ^[2]

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1. Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)
2. (China)

We present a theoretical study on the absorption of the surface acoustic waves (SAWs) by Dirac electrons in topological insulator (TI) thin films (TITFs). We find that due to momentum and energy conservation laws, the absorption of the SAWs in TITFs can only be achieved via intra-band electronic transitions. The strong absorption can be observed up to sub-terahertz frequencies. With increasing temperature, the absorption intensity increases significantly and the cut-off frequency is blue-shifted. More interestingly, we find that the absorption of the SAWs by the TITFs can be markedly enhanced by the tunable subgap in the Dirac energy spectrum of the TI surface states. Such a subgap is absent in conventional two-dimensional electron gases (2DEGs) and in the gapless Dirac 2DEG such as graphene. This study is pertinent to the exploration of the acoustic properties of TIs and to potential application of TIs as tunable SAW devices working at hypersonic frequencies.

• OSTI ID: 22318022
• Journal Information: Applied Physics Letters, Vol. 105, Issue 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION
ELECTRON GAS
GRAPHENE
SOUND WAVES
SURFACES
THIN FILMS
TWO-DIMENSIONAL CALCULATIONS