Thermoelectric properties of 3D topological insulator: Direct observation of topological surface and its gap opened states

Stephane Yu Matsushita, Khuong Kim Huynh, Harukazu Yoshino, Ngoc Han Tu, Yoichi Tanabe, Katsumi Tanigaki

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

We report thermoelectric (TE) properties of topological surface Dirac states (TSDS) in three-dimensional topological insulators (3D-TIs) purely isolated from the bulk by employing single-crystal Bi2-xSbxTe3-ySey films epitaxially grown in the ultrathin limit. Two intrinsic nontrivial topological surface states, a metallic TSDS (m-TSDS) and a gap-opened semiconducting topological state (g-TSDS), are successfully observed by electrical transport, and important TE parameters [electrical conductivity (σ), thermal conductivity (κ), and thermopower (S)] are accurately determined. Pure m-TSDS gives S=-44μVK-1, which is an order of magnitude higher than those of the conventional metals and the value is enhanced to -212μVK-1 for g-TSDS. It is clearly shown that the semiclassical Boltzmann transport equation (SBTE) in the framework of constant relaxation time (τ) most frequently used for conventional analysis cannot be valid in 3D-TIs and strong energy dependent relaxation time τ(E) beyond the Born approximation is essential for making intrinsic interpretations. Although σ is protected on the m-TSDS, κ is greatly influenced by the disorder on the topological surface, giving a dissimilar effect between topologically protected electronic conduction and phonon transport.

Original languageEnglish
Article number054202
JournalPhysical Review Materials
Volume1
Issue number5
DOIs
Publication statusPublished - 2017 Oct 13

ASJC Scopus subject areas

  • Materials Science(all)
  • Physics and Astronomy (miscellaneous)

Fingerprint Dive into the research topics of 'Thermoelectric properties of 3D topological insulator: Direct observation of topological surface and its gap opened states'. Together they form a unique fingerprint.

Cite this