Quantum oscillation beyond the quantum limit in pseudospin Dirac materials

TL;DR

This paper introduces a novel mechanism for quantum oscillations in Dirac materials beyond the quantum limit, characterized by larger amplitude and periodicity in magnetic field, not explained by traditional models.

Contribution

It proposes a new mechanism involving Landau level inversion due to pseudospin and real-spin interactions, explaining unexpected oscillation behaviors in high magnetic fields.

Findings

Oscillations are larger in amplitude than Shubnikov--de Haas oscillations.

Oscillations are periodic in magnetic field B, not 1/B.

Period of oscillation independent of Fermi energy.

Abstract

Recently, many unexpected fine structures in electric, magnetic, and thermoelectric responses at extremely magnetic fields in topological materials have attracted tremendous interest. We propose a new mechanism of quantum oscillation beyond the strong-field quantum limit for Dirac fermions. The amplitude of the oscillation is far larger than the usual Shubnikov--de Haas oscillation. The oscillation tends to be periodic in the magnetic field B, instead of 1/B. The period of the oscillation does not depend on the Fermi energy. These behaviors cannot be described by the famous Lifshitz-Kosevich formula. The oscillation arises from a mechanism that we refer to as the inversion of the lowest Landau level, resulted from the competition between the pseudospin Dirac-type Landau levels and real-spin Zeeman spitting beyond the quantum limit. This inversion gives rise to the oscillation of the Fermi energy and conductivity at extremely large magnetic fields. This mechanism will be useful for understanding the unexpected fine structures observed in the strong-field quantum limit in Dirac materials.