Quantum Oscillation from In-gap States and non-Hermitian Landau Level Problem

TL;DR

This paper investigates quantum oscillations in small-gap insulators with in-gap states caused by disorder, using a non-Hermitian Landau level approach to connect experimental observations with theoretical models.

Contribution

It introduces a non-Hermitian Landau level framework to analyze quantum oscillations from in-gap states, providing analytical formulas linking oscillation features to material parameters.

Findings

Oscillation period depends on the Fermi surface area without hybridization gap.

Oscillation amplitude is analytically related to the indirect band gap, scattering rates, and temperature.

Effective mass and Dingle factor are controlled by scattering rates and the indirect band gap, respectively.

Abstract

Motivated by recent experiments on Kondo insulators, we theoretically study quantum oscillations from disorder-induced in-gap states in small-gap insulators. By solving a non-Hermitian Landau level problem that incorporates the imaginary part of electron's self-energy, we show that the oscillation period is determined by the Fermi surface area in the absence of the hybridization gap, and derive an analytical formula for the oscillation amplitude as a function of the indirect band gap, scattering rates, and temperature. Over a wide parameter range, we find that the effective mass is controlled by scattering rates, while the Dingle factor is controlled by the indirect band gap. We also show the important effect of scattering rates in reshaping the quasiparticle dispersion in connection with angle-resolved photoemission measurements on heavy fermion materials.