Magnetoquantum Oscillations in the Specific Heat of a Topological Kondo Insulator

TL;DR

This paper reports the first observation of magnetoquantum oscillations in the specific heat of the topological Kondo insulator SmB6, providing evidence for their bulk thermodynamic origin and intrinsic nature.

Contribution

It demonstrates that MQO in SmB6 are intrinsic and bulk-related by measuring specific heat, with larger effective masses than previously observed in torque measurements.

Findings

MQO observed in specific heat measurements.

Effective masses are larger than previous reports.

Results support intrinsic bulk origin of MQO.

Abstract

Surprisingly, magnetoquantum oscillations (MQO) characteristic of a metal with a Fermi surface have been observed in measurements of the topological Kondo insulator SmB6. As these MQO have only been observed in measurements of magnetic torque (dHvA) and not in measurements of magnetoresistance (SdH), a debate has arisen as to whether the MQO are an extrinsic effect arising from rare-earth impurities, defects, and/or aluminum inclusions or an intrinsic effect revealing the existence of charge-neutral excitations. We report here the first observation of magnetoquantum oscillations in the low-temperature specific heat of SmB6. The observed frequencies and their angular dependence for these flux-grown samples are consistent with previous results based on magnetic torque for SmB6 but the inferred effective masses are significantly larger than previously reported. Such oscillations can only be observed if the MQO are of bulk thermodynamic origin; the measured magnetic-field dependent oscillation amplitude and effective mass allow us to rule out suggestions of an extrinsic, aluminium inclusion-based origin for the MQO.