Role of K/Bi disorder in the electronic structure of β-K2Bi8Se13

Khang Hoang, Aleksandra Tomic, S. D. Mahanti, Theodora Kyratsi, Duck-Young Chung, S. H. Tessmer, and Mercouri G. Kanatzidis
Phys. Rev. B 80, 125112 – Published 15 September 2009

Abstract

We have carried out tunneling spectroscopy and first-principles studies for β-K2Bi8Se13, a promising thermoelectric material with partially disordered mixed K/Bi sites. The tunneling data, obtained with a scanning tunneling microscope (STM), show that the system is a semiconductor with a band gap of 0.4eV and band-tail states near the valence-band top and the conduction-band bottom. First-principles calculations, on the other hand, show that β-K2Bi8Se13 can be semimetallic or semiconducting depending on the arrangements of the K and Bi atoms in the mixed sites. The electronic structure of β-K2Bi8Se13 near the band-gap region is largely determined by unbonded Sep states and states associated with strained bonds which are present due to K/Bi disorder and by the Bip-Sep hybridization which tends to drive the system toward metallicity. Among the different K/Bi arrangements investigated, we have identified a structural model (quasidisordered structure) that is able to satisfactorily reproduce the atomic and electronic structures of β-K2Bi8Se13; i.e., the local composition in the mixed channels as observed experimentally and the band gap and tails as seen in the STM measurements. We argue that transport properties of β-K2Bi8Se13 can be qualitatively understood in terms of the electronic structure obtained in calculations using the above structural model.

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  • Received 30 March 2009

DOI:https://doi.org/10.1103/PhysRevB.80.125112

©2009 American Physical Society

Authors & Affiliations

Khang Hoang1, Aleksandra Tomic2, S. D. Mahanti2,*, Theodora Kyratsi3, Duck-Young Chung4, S. H. Tessmer2, and Mercouri G. Kanatzidis4,5

  • 1Materials Department, University of California, Santa Barbara, California 93106, USA
  • 2Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
  • 3Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia 1678, Cyprus
  • 4Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
  • 5Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA

  • *Corresponding author; mahanti@pa.msu.edu

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Vol. 80, Iss. 12 — 15 September 2009

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