Mean field exact solutions showing charge density wave crossover at low fillings in the fractional quantum Hall regime

TL;DR

This paper develops an analytical framework for mean field states in the fractional quantum Hall regime, revealing a charge density wave crossover near filling factor 1/7 and suggesting possible phase transitions.

Contribution

It introduces exact solutions for mean field states at rational fillings, including new charge density distributions and a crossover between Hall Crystal and Wigner crystal states.

Findings

Identifies a charge density wave crossover near filling 1/7.

Provides analytic expressions for states at filling factors of the form 1/q.

Suggests phase transitions between different crystalline states as electron density varies.

Abstract

A general analytical framework for the determination of the mean field states at arbitrary rational filling factors for the 2DEG in FQHE regime is given. Its use allows to obtain analytic expressions for the solutions at filling factors of the form $\nu=1/q$ for arbitrary odd $q$. The analysis can be performed for two general classes of states characterized by $\gamma=1$ or $\gamma={1/2}$ particles per unit cell. Instead of the periodic peaks of the Wigner solid solution, the new states show electron densities forming percolating ridges that may favor an energy decrease through correlated ring of exchange contributions. Therefore, we estimate that they can realize mean field versions of the so called Hall Crystal (HC) states. The obtained analytic HC solution shows the same crystalline symmetry that the corresponding WC state in its class $\gamma=1$, but a qualitatively different charge density distribution. The energy dependence of the corresponding HC and WC states on the filling factor is also evaluated here for the class $\gamma=1/2$. The results show a crossover between HC state and the Wigner crystal, close to filling 1/7. Therefore, transitions may occur from one to the other as the electron density is varied. This result is consistent with recent experimental findings.