Quantum oscillations in the zeroth Landau Level and the serpentine Landau fan

TL;DR

This paper uncovers a novel quantum oscillation mechanism in nodal semimetals caused by Landau levels periodically closing their gap, revealing unique periodicity and temperature dependence linked to a Rabi model analogy.

Contribution

It introduces zero Landau level quantum oscillations in nodal semimetals and connects the Landau spectrum to the Rabi model, highlighting a serpentine pattern of Landau levels.

Findings

Identification of ZQOs driven by Landau level gap closures

Exact solution showing intertwined Landau levels in a serpentine pattern

Proposal of topological crystalline insulators as natural ZQO platforms

Abstract

We identify an unusual mechanism for quantum oscillations in nodal semimetals, driven by a single pair of Landau levels periodically closing their gap at the Fermi energy as a magnetic field is varied. These `zero Landau level' quantum oscillations (ZQOs) appear in the nodal limit where the zero-field Fermi volume vanishes, and have distinctive periodicity and temperature dependence. We link the Landau spectrum of a two-dimensional (2D) nodal semimetal to the Rabi model, and show by exact solution that across the entire Landau fan, pairs of opposite-parity Landau levels are intertwined in a `serpentine' manner. We propose 2D surfaces of topological crystalline insulators as natural settings for ZQOs, and comment on implications for anomaly physics in 3D nodal semimetals.