Thermoelectric Transport by Surface States in Bi2Se3-Based Topological Insulator Thin Films**Supported by the National Natural Science Foundation of China under Grant No 11304316, the Ministry of Science and Technology of China under Grant No 2011YQ130018, the Department of Science and Technology of Yunnan Province, and the Chinese Academy of Sciences.

Abstract

We develop a tractable theoretical model to investigate the thermoelectric (TE) transport properties of surface states in topological insulator thin films (TITFs) of Bi2Se3 at room temperature. The hybridization between top and bottom surface states in the TITF plays a significant role. With the increasing hybridization-induced surface gap, the electrical conductivity and electron thermal conductivity decrease while the Seebeck coefficient increases. This is due to the metal-semiconductor transition induced by the surface-state hybridization. Based on these TE transport coefficients, the TE figure-of-merit ZT is evaluated. It is shown that ZT can be greatly improved by the surface-state hybridization. Our theoretical results are pertinent to the exploration of the TE transport properties of surface states in TITFs and to the potential application of Bi2Se3-based TITFs as high-performance TE materials and devices.