Re-entrant behavior of the ν=4/3 fractional quantum Hall effect in a front-and-back-gated 2D hole gas

Abstract

The fractional quantum Hall (FQH) effect of a two-dimensional hole gas has been studied in a modulation-doped quantum well (QW) with front and back gates. We found that the ν=4/3 state shows intriguing re-entrant behavior; as the hole density was varied with the front gate, the ν=4/3 state was observed to weaken in two regions of magnetic field. Temperature-dependent measurements reveal that the energy gap Δ4/3 exhibits two minima as a function of magnetic field. This double re-entrant behavior contrasts markedly with the spin transition of electron systems which occurs around only one critical magnetic field. Results for different back-gate biases, i.e., for different Landau-level (LL) structures for the same density, are presented to discuss the effect of the valence-band LL structure.