Aperiodic quantum oscillations of particle-hole asymmetric Dirac cones

TL;DR

This paper presents experimental and theoretical analysis of unusual high-field quantum oscillations in a Dirac cone system, revealing anomalies linked to particle-hole asymmetry and ruling out alternative causes.

Contribution

It provides the first detailed investigation of a-(BEDT-TTF)2I3 Dirac cones under pressure, highlighting the role of intrinsic asymmetries in quantum oscillation behavior.

Findings

Anomalies in SdH oscillations at high magnetic fields above 7 T.

Particle-hole asymmetric distortion explains the loss of periodicity.

Results are consistent across samples with different Fermi levels.

Abstract

We report experimental measurements and theoretical analysis of Shubnikov-de Haas (SdH) oscillations in a Dirac cone system: the a-(BEDT-TTF)2I3 organic metal under hydrostatic pressure. The measured SdH oscillations reveal anomalies at high magnetic fields B where the 1/B oscillations periodicity is lost above 7 T. We interpret these unusual results within a theoretical model that takes into account intrinsic distortions of the a-(BEDT-TTF)2I3 Dirac cones such as a parabolic particle-hole asymmetric correction. Others possible causes, such as a cone tilting or a Zeeman effect, are carefully ruled out. The observations are consistent among a-(BEDT-TTF)2I3 samples with different Fermi levels.