Breakdown of Particle-Hole Symmetry in the Lowest Landau Level Revealed by Tunneling Spectroscopy

TL;DR

This study uses tunneling spectroscopy to reveal a breakdown of particle-hole symmetry in the lowest Landau level, showing distinct spectral features at different filling factors, which challenges the expected symmetry in quantum Hall systems.

Contribution

It demonstrates a qualitative difference in tunneling spectra between $ u=1/2$ and $ u=3/2$, indicating particle-hole symmetry breaking in the lowest Landau level.

Findings

Single peak at $ u=1/2$ with Coulomb pseudogap

Double peak at $ u=3/2$ indicating asymmetry

No similar effect at $ u=5/2$ and 7/2 in higher Landau levels

Abstract

Tunneling measurements on 2D electron gases at high magnetic field reveal a qualitative difference between the two spin sublevels of the lowest Landau level. While the tunneling current-voltage characteristic at filling factor $\nu = 1/2$ is a single peak shifted from zero bias by a Coulomb pseudogap, the spectrum at $\nu=3/2$ shows a well-resolved double peak structure. This difference is present regardless of whether $\nu =1/2$ and $\nu = 3/2$ occur at the same or different magnetic fields. No analogous effect is seen at $\nu = 5/2$ and 7/2 in the first excited Landau level.