Bi 2Te 1.6S 1.4: A topological insulator in the tetradymite family

Huiwen Ji, J. M. Allred, M. K. Fuccillo, M. E. Charles, M. Neupane, L. A. Wray, M. Z. Hasan, R. J. Cava

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Abstract

We describe the crystal growth, crystal structure, and basic electrical properties of Bi 2Te 1.6S 1.4, which incorporates both S and Te in its tetradymite quintuple layers in the motif -[Te 0.8S 0.2]-Bi-S-Bi-[Te 0.8S 0.2]-. This material differs from other tetradymites studied as topological insulators due to the increased ionic character that arises from its significant S content. Bi 2Te 1.6S 1.4 forms high quality crystals from the melt and is the S-rich limit of the ternary Bi-Te-S γ-tetradymite phase at the melting point. The native material is n type with a low resistivity; Sb substitution, and with adjustment of the Te to S ratio, results in a crossover to p type and resistive behavior at low temperatures. An angle-resolved photoemission study shows that topological surface states are present, with the Dirac point more exposed than it is in Bi 2Te 3 and similar to that seen in Bi 2Te 2Se. Single crystal structure determination indicates that the S in the outer chalcogen layers is closer to the Bi than the Te, and therefore that the layers supporting the surface states are corrugated on the atomic scale.

Original languageEnglish (US)
Article number201103
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume85
Issue number20
DOIs
StatePublished - May 15 2012

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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