Realistic Calculations of Correlated Incompressible Electronic States in GaAs--Al_{x}Ga_{1-x}As Heterostructures and Quantum Wells

TL;DR

This study performs realistic finite-size calculations of fractional quantum Hall states in GaAs-AlGaAs heterostructures, accurately estimating pseudopotentials and excitation gaps, and compares results with experimental data showing excellent agreement.

Contribution

It introduces a self-consistent LDA approach to determine pseudopotentials for realistic quantum well systems, improving the accuracy of fractional quantum Hall state modeling.

Findings

Large overlap with Laughlin state at experimental densities

Calculated excitation gaps match experimental measurements

Realistic pseudopotentials improve modeling accuracy

Abstract

We perform an exact spherical geometry finite-size diagonalization calculation for the fractional quantum Hall ground state in three different experimentally relevant GaAs-Al_{x}Ga_{1-x}As systems: a wide parabolic quantum well, a narrow square quantum well, and a heterostructure. For each system we obtain the Coulomb pseudopotential parameters entering the exact diagonalization calculation by using the realistic subband wave function from a self-consistent electronic structure calculation within the local density approximation (LDA) for a range of electron densities. We compare our realistic LDA pseudopotential parameters with those from widely used simpler model approximations in order to estimate the accuracies of the latter. We also calculate the overlap between the exact numerical ground state and the analytical Laughlin state as well as the excitation gap as a function of density. For the three physical systems we consider the calculated overlap is found to be large in the experimental electron density range. We compare our calculated excitation gap energy to the experimentally obtained activated transport energy gaps after subtracting out the effect of level broadening due to collisions. The agreement between our calculated excitation gaps and the experimental measurements is excellent.