Measurement of photoluminescence spectral linewidth of a GaAs quantum well in perpendicular electric fields: Evidence of a crossover from trions to an electron-hole gas

Abstract

By measuring the photoluminescence linewidth of a GaAs quantum well under perpendicular electric fields, we have traced the variation of the effective radius a * of a charged exciton (trion) as a function of electron density. The a * increases sharply above a critical density n s = 2 × 10 14 m −2 , which is consistent with the decrease of the screening length predicted by nonlinear-screening theory. Our analysis shows that the crossover from trions to the two-dimensional electron gas plus hole is generated by Coulomb screening in the high-electron-density regime, eliminating the possible mechanism by the trion localization effect due to the single-electron localization.

Variational and diffusion quantum Monte Carlo calculations with the CASINO code

“…The crossover between high-density Fermi-edgesingularity behavior dominated by many-body correlations and low-density behavior characterized by the presence of isolated excitons and trions has been investigated experimentally in high-mobility 2D HEGs in GaAs/AlGaAs and InGaAs/InAlAs heterostructures. [178][179][180][181] Rapid changes in line shapes and transition energies in absorption and photoluminescence spectra of a gated modulation-doped quantum well allow experimentalists to locate a critical "crossover" density.…”

“…The arrow marks the density range over which an evolution from a collective state characterized by a Fermi-edge singularity (FES) to a trion-in-HEG phase was experimentally detected, 178 and the other symbols flag regions of phase space which have been experimentally characterized as being in the crossover regime. [179][180][181] to the energy per particle c (r s ) of the 2D HEG as a function of density. 182 Hence Spink et al were able to calculate the correction to the quasiparticle gap due to the finite concentration of electrons in the conduction band and the resulting electron-hole correlation.…”

Photoluminescence fine structures in the fractional quantum Hall effect regime

“…The PL was detected with a Spex 1404 double monochromator equipped with a liquid-nitrogen-cooled charge-coupled-device detector. Details of the experiments can be found elsewhere [31,32].…”