Direct observation of surface state thermal oscillation in SmB6 oscillators

TL;DR

This paper reports the first direct measurement of temperature oscillations in the surface state of SmB6, confirming theoretical models and advancing the development of high-frequency SmB6 oscillators.

Contribution

It provides the first experimental observation of surface state temperature oscillations in SmB6, validating the theoretical thermal-electronic dynamics model.

Findings

Measured surface state temperature oscillations match theoretical predictions.

Supports the validity of the thermal-electronic coupled model.

Enables development of higher-frequency SmB6 oscillators.

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 4K. 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 non-linear 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, hasn't 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 RuO micro-thermometer. 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 SmB6oscillators at higher frequencies.