Quantum oscillations in interaction-driven insulators

TL;DR

This paper investigates quantum oscillations in interaction-driven insulators, revealing how magnetic field-induced oscillations can be used to probe bandgap and interaction effects, especially in Kondo and excitonic insulators.

Contribution

It demonstrates that in interaction-driven insulators, quantum oscillations are influenced by oscillating self-consistent parameters, offering new ways to measure bandgap and interaction effects.

Findings

Lowest harmonic of magnetization oscillations remains unaffected by interactions at low temperatures.

Higher harmonics are dominated by interaction effects, providing a method to measure these interactions.

Quantum oscillations can reveal the size of the bandgap even in insulators with strong interactions.

Abstract

In recent years it has become understood that quantum oscillations of the magnetization as a function of magnetic field, long recognized as phenomena intrinsic to metals, can also manifest in insulating systems. Theory has shown that in certain simple band insulators, quantum oscillations can appear with a frequency set by the area traced by the minimum gap in momentum space, and are suppressed for weak fields by an intrinsic "Dingle damping" factor reflecting the size of the bandgap. Here we examine quantum oscillations of the magnetization in excitonic and Kondo insulators, for which interactions play a crucial role. In models of these systems, self-consistent parameters themselves oscillate with changing magnetic field, generating additional contributions to quantum oscillations. In the low-temperature, weak-field regime, we find that the lowest harmonic of quantum oscillations of the magnetization are unaffected, so that the zero-field bandgap can still be extracted by measuring the Dingle damping factor of this harmonic. However, these contributions dominate quantum oscillations at all higher harmonics, thereby providing a route to measure this interaction effect.