Anomalously high electronic thermal conductivity and Lorenz ratio in Bi2Te3 nanoribbons far from the bipolar condition

Hwan Sung Choe, Jiachen Li, Wenjing Zheng, Jaejun Lee, Joonki Suh, Frances I. Allen, Huili Liu, Heon Jin Choi, Wladek Walukiewicz, Haimei Zheng, Junqiao Wu

Research output: Contribution to journalArticle

Abstract

The Lorenz number (L) of a conductor is the ratio between its electronic thermal conductivity and electrical conductivity. It takes the Sommerfeld value of L0=π2/3kB/e2 in simple, metallically electronic systems where charge and heat are both carried by the same group of quasi-particles that experience elastic scattering. Higher values of L than L0 are possible in semiconductors where both electrons and holes co-exist at high densities, that is, in bipolar conduction. As a narrow-bandgap semiconductor, Bi2Te3 exhibits L > L0 which has been generally attributed to such bipolar conduction mechanisms. However, in this work, we report that L > L0 is still observed in individual, single-crystal Bi2Te3 nanoribbons even at low temperatures and when degenerately doped, that is, far from the bipolar conduction condition. This discovery calls for different mechanisms to explain the unconventional electronic thermal transport behavior in Bi2Te3.

Original languageEnglish
Article number152101
JournalApplied Physics Letters
Volume114
Issue number15
DOIs
Publication statusPublished - 2019 Apr 15

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)

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    Choe, H. S., Li, J., Zheng, W., Lee, J., Suh, J., Allen, F. I., Liu, H., Choi, H. J., Walukiewicz, W., Zheng, H., & Wu, J. (2019). Anomalously high electronic thermal conductivity and Lorenz ratio in Bi2Te3 nanoribbons far from the bipolar condition. Applied Physics Letters, 114(15), [152101]. https://doi.org/10.1063/1.5092221