HYSTERESIS IN THE QUANTUM HALL REGIMES IN ELECTRON DOUBLE-QUANTUM-WELL STRUCTURES

摘要

We present in this paper the experimental results of transport hysteresis in an extremely imbalanced electron double-quantum-well (DQW) structure. The ratio of the top layer density (n_(top)) to bottom layer density (n_(bot)) is continuously tuned by applying voltage to a front gate. Under a condition when the top layer is nearly depleted (n_(top) ～ 3 x 10~(10) cm~(-2)) while the bottom layer remains at n_(bot) = 1.9 x 10~(11) cm~(-2), the hysteresis is absent in the B sweeps as long as the total Landau level filling ν < 1 and the 2D electron systems are in the fractional quantum Hall effect regime. Surprisingly, a large hysteresis is observed during the gate sweeps at the same values of B and n_(top). We attribute this unexpected hysteresis to the formation of an insulating state, probably a weakly pinned Wigner solid state, in the top layer.