Terahertz transmission studies of the topological Kondo insulator candidate SmB$_6$

ORAL

Abstract

The Kondo insulator SmB$_6$ has long been known to display anomalous transport behavior at low temperatures (T$<10$ K) and high pressures. At low temperatures, a plateau is observed in the resistivity, contrary to the divergence expected for a normal Kondo insulator. Recent theoretical calculations suggest that SmB$_6$ may be the first topological Kondo insulator, a material with a Kondo insulating bulk, but topologically protected metallic surface states.\footnote{M. Dzero \textit{et al.}, Phys. Rev. Lett. \textbf{104}, 106408 (2010)} Here, time domain terahertz spectroscopy (TDTS) is used to investigate the temperature dependent low frequency optical conductivity of single crystals of SmB$_6$. We find evidence for a substantial bulk conductivity at a frequency of a few hundred GHz, which challenges the notion of this material as having a clean gap. The evidence for topological surface states and their properties will be discussed.

*Work supported by The Institute of Quantum Matter under DOE grant DE-FG02-08ER46544 and by the Gordon and Betty Moore Foundation through Grant GBMF2628.

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Authors

  • Nicholas J. Laurita

    • The Institute for Quantum Matter, Department of Physics \& Astronomy, The Johns Hopkins University, Baltimore, MD 21218

  • Christopher M. Morris

    • The Institute for Quantum Matter, Department of Physics \& Astronomy, The Johns Hopkins University, Baltimore, MD 21218

  • Seyed Koopayeh

    • The Institute for Quantum Matter, Department of Physics \& Astronomy, The Johns Hopkins University, Baltimore, MD 21218

  • Patrick Cottingham

    • The Institute for Quantum Matter, Department of Physics \& Astronomy, The Johns Hopkins University, Baltimore, MD 21218

  • W. Adam Phelan

    • The Institute for Quantum Matter, Department of Physics \& Astronomy, The Johns Hopkins University, Baltimore, MD 21218

  • Leslie Schoop

    • The Institute for Quantum Matter, Department of Physics \& Astronomy, The Johns Hopkins University, Baltimore, MD 21218

  • Tyrel M. McQueen

    • The Institute for Quantum Matter, Department of Physics \& Astronomy, The Johns Hopkins University, Baltimore, MD 21218

  • N. Peter Armitage

    • The Institute for Quantum Matter, Department of Physics \& Astronomy, The Johns Hopkins University, Baltimore, MD 21218