Direct observation of surface-state thermal oscillations in SmB6 oscillators

Brian Casas, Alex Stern, Dmitry K. Efimkin, Zachary Fisk, and Jing Xia
Phys. Rev. B 97, 035121 – Published 10 January 2018

Abstract

SmB6 is a mixed valence Kondo insulator that exhibits a sharp increase in resistance following an activated behavior that levels off and saturates below 4 K. This behavior can be explained by the proposal of SmB6 representing a new state of matter, a topological Kondo insulator, in which a Kondo gap is developed, and topologically protected surface conduction dominates low-temperature transport. Exploiting its nonlinear dynamics, a tunable SmB6 oscillator device was recently demonstrated, where a small dc current generates large oscillating voltages at frequencies from a few Hz to hundreds of MHz. This behavior was explained by a theoretical model describing the thermal and electronic dynamics of coupled surface and bulk states. However, a crucial aspect of this model, the predicted temperature oscillation in the surface state, has not been experimentally observed to date. This is largely due to the technical difficulty of detecting an oscillating temperature of the very thin surface state. Here we report direct measurements of the time-dependent surface-state temperature in SmB6 with a RuO2 microthermometer. Our results agree quantitatively with the theoretically simulated temperature waveform, and hence support the validity of the oscillator model, which will provide accurate theoretical guidance for developing future SmB6 oscillators at higher frequencies.

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  • Received 26 March 2017
  • Revised 9 December 2017

DOI:https://doi.org/10.1103/PhysRevB.97.035121

©2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Brian Casas1, Alex Stern1, Dmitry K. Efimkin2, Zachary Fisk1, and Jing Xia1,*

  • 1Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697, USA
  • 2Department of Physics, University of Texas, Austin, Austin, Texas 78712, USA

  • *Corresponding author: xia.jing@uci.edu

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Issue

Vol. 97, Iss. 3 — 15 January 2018

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