Magneto-Optics in the Fractional Quantum Hall and Electron Solid Regimes

Abstract

Optical emission from the recombination of two-dimensional electrons and valence band holes has been studied in ultra-high mobility GaAs single quantum wells and single heterojunctions. At integer Hall plateaus, the electrons cannot react to the hole, and the polarization dependence of shifts in the electron-hole recombination energy are used to determine the mechanisms of changes in the many-body electron screening. At precisely the position of the v = 2/3 fractional quantum Hall state, a sharp blue shift is observed, which is independent of the details of the electron-hole interaction, pointing to the differences in electron response in the integer and fractional quantum Hall cases. Additionally, the shift is accompanied by a decrease in the upper-spin-state emission, indicating the polarized nature of the electronic ground state. At v = 1/3 and 2/5 a splitting in the main emission peak occurs, with the higher energy component becoming dominant at higher magnetic fields. Recent results have been obtained in the regime of the electron solid, where simultaneous optical and non-linear transport measurements have been made to B=20T and T=36mK. The data shown an overall decrease in the recombination intensity and a shift in spectral weight to the low energy features. Weak variations in the luminescence occurs between 200mK and 38mK at filling factors v ≤ 1/5 while simultaneous measurement of the non-linear transport shows a significant qualitative difference.