Electronic structure of Na$_3$Bi near the Dirac point: Optical measurements

ORAL

Abstract

The first optical characterization of Na$_3$Bi is reported. Reflection measurements on c-plane oriented single-crystals, over the spectral range from 3 mev to 2.5 eV and temperature ranging from 8 to 250K, show a low frequency response consistent with the low doping level $n\sim10^{17} \text{ cm}^{-1}$. The number of observed phonons in the optical spectra is $>$5, which eliminates the P6$_{3}$/mmc symmetry since point group analysis indicates only 2 IR active phonons. A striking, strongly temperature dependent plasma edge reverses direction at $T\sim100$K. The behavior is consistent with thermal population effects in a Dirac cone permitting an estimation of the Fermi level. The Lifshitz gap energy is reported.

*UMD supported by NSF (DMR-1104343), Princeton supported by the ARO MURI on topological insulators (Grant No. W911NF-12-1-0461) and ARO (W911NF-11-1-0379) and MRSEC program (NSF-DMR-0819860 and DOE DE-FG-02-05ER46200), NU supported by the U.S.D.O.E.

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Authors

  • Gregory S. Jenkins

    • U. of Md College Park

  • A. B. Sushkov

    • U. of Md College Park

  • R. L. Carey

    • U. of Md College Park

  • H. D. Drew

    • U. of Md College Park

  • J. Krizan

    • Princeton U.

  • S. Kushwaha

    • Princeton U.

  • R. Cava

    • Princeton U.

  • Tay-Rong Chang

    • National Tsing Hua U.

  • Horng-Tay Jeng

    • National Tsing Hua U.

  • H. Lin

    • NUS

  • C. Lane

    • Northeastern U.

  • B. Barbiellini

    • Northeastern U.

  • A. Bansil

    • Northeastern U.