Terahertz transmission and reflection 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 logarithmic 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 optical conductivity of single crystals of SmB$_6$. A saturation of the transmission is observed associated with the resistance plateau as the bulk becomes insulating. A secondary bulk conduction mechanism remains down to the lowest measured temperature, 1.6 K. Additionally, FTIR measurements have been performed that show the Kondo gap of SmB$_6$ opening at low temperatures.

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

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Authors

  • Christopher M. Morris

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

  • N.J. Laurita

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

  • S. Koopayeh

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

  • P. Cottingham

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

  • W.A. Phelan

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

  • L. Schoop

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

  • T.M. McQueen

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

  • N.P. Armitage

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