Chemical potential asymmetry and quantum oscillations in insulators

TL;DR

This paper develops a theory of quantum oscillations in particle-hole symmetric insulators, revealing how oscillation behavior depends on temperature and chemical potential position within the gap, with unique phase and amplitude features.

Contribution

It introduces a novel theoretical framework for understanding quantum oscillations in insulators with arbitrary band dispersion, highlighting effects of chemical potential asymmetry.

Findings

Oscillations are temperature-independent when chemical potential is in the middle of the gap.

Asymmetric chemical potential causes oscillations to vanish at a critical field and then reappear with a phase shift.

Distinct temperature dependencies are observed for magnetization, susceptibility, and resistivity.

Abstract

We present a theory of quantum oscillations in insulators that are particle-hole symmetric and non-topological but with arbitrary band dispersion, at both zero and non-zero temperature. At temperatures $T$ less than or comparable to the gap, the dependence of oscillations on $T$ is markedly different from that in metals and depends crucially on the position of the chemical potential $\mu$ in the gap. If $\mu$ is in the middle of the gap, oscillations do not change with $T$; however, if $\mu$ is asymmetrically positioned in the gap, surprisingly, oscillations go to zero at a critical value of the inverse field determined by $T$ and $\mu$ and then change their phase by $\pi$ and grow again. Additionally, the temperature dependence is different for quantities derived from the grand canonical potential, such as magnetization and susceptibility, and those derived from the density of states, such as resistivity. However, the non-trivial features arising from asymmetric $\mu$ are present in both.