# Fluctuations and magnetoresistance oscillations near the half-filled Landau level

## TL;DR

This paper theoretically investigates magnetoresistance oscillations near the half-filled Landau level using Dirac composite fermion theory, incorporating gauge field fluctuations to explain experimental observations and propose new measurement methods.

## Contribution

It extends previous mean-field studies by including gauge fluctuations, revealing a fluctuation-induced mass that shifts oscillation minima and aligns theory with experiments.

## Key findings

- Gauge fluctuations generate a mass for composite fermions.
- Mass causes a shift in oscillation minima, matching experiments.
- Oscillation amplitude's temperature dependence offers a new measurement approach.

## Abstract

We study theoretically the magnetoresistance oscillations near a half-filled lowest Landau level ($\nu = 1/2$) that result from the presence of a periodic one-dimensional electrostatic potential. We use the Dirac composite fermion theory of Son [Phys. Rev. X 5 031027 (2015)], where the $\nu=1/2$ state is described by a $(2+1)$-dimensional theory of quantum electrodynamics. We extend previous work that studied these oscillations in the mean-field limit by considering the effects of gauge field fluctuations within a large flavor approximation. A self-consistent analysis of the resulting Schwinger--Dyson equations suggests that fluctuations dynamically generate a Chern-Simons term for the gauge field and a magnetic field-dependent mass for the Dirac composite fermions away from $\nu=1/2$. We show how this mass results in a shift of the locations of the oscillation minima that improves the comparison with experiment [Kamburov et. al., Phys. Rev. Lett. 113, 196801 (2014)]. The temperature-dependent amplitude of these oscillations may enable an alternative way to measure this mass. This amplitude may also help distinguish the Dirac and Halperin, Lee, and Read composite fermion theories of the half-filled Landau level.