Fractional quantum Hall effect in bilayer two-dimensional hole-gas systems

Abstract

We have studied the fractional and integer quantum Hall effect in high mobility double layer 2D hole gas systems. The large hole effective mass inhibits tunneling, allowing us to investigate the regime in which the interlayer and intralayer interactions are comparable without significant interlayer tunneling

Bias-voltage-induced phase transition in bilayer quantum Hall ferromagnets

“…This is the first principle conclusion of this work and results from the property that pseudospin-waves around the ν = 1 quantum Hall state are stiffened by the bias-voltage. 21,[25][26][27] The emergence of the ν = 1 quantum Hall plateau had been predicted by Brey et al 19 when the applied bias-voltage exceeds the critical bias-voltage, ∆ v ≥ ∆ vc , and all charge is in one layer. On the other hand, our calculations predict the emergence of the ν = 1 plateau for ∆ v < ∆ vc .…”

“…13 We see that the difference between the mean-field and the renormalized stiffness decreases as the bias-voltage increases, which is consistent with the fact that the bias-voltage stabilizes the collective excitations. 21,[25][26][27] V. SUMMARY…”

Anomalous stability of ν = 1 bilayer quantum Hall state

“…We hereafter refer to the QH states as "balanced QH states" when the densities are equal, and as "unbalanced QH states" when they are not equal. Experiments have so far been made extensively on balanced QH states [2,7], and only limited works have been done on the unbalanced QH states [8,9]. The study of unbalanced QH states reveals its character: For instance, if the QH state is stabilized by the energy gap ∆ SAS , it decays as the system becomes unbalanced.…”

Negative effective mass mechanism of negative differential drift velocity and terahertz generation

“…It is true that such high values of hole mobility are reached either in quasi-triangle QWs [28]- [31] or in very thick square QWs [29], [34], where the hole gas is of the same structure as in the triangle wells. [Note that very high hole mobilities are also measured in double hole gas systems [34], [35], in which p-GaAs QWs are separated by AlGaAs barriers. In [35], mobilities in each of 15-nm-thick wells are equal to 10 cm /Vs (T 30 mK) at the barrier thickness 2.0-3.5 nm.]…”

“…[Note that very high hole mobilities are also measured in double hole gas systems [34], [35], in which p-GaAs QWs are separated by AlGaAs barriers. In [35], mobilities in each of 15-nm-thick wells are equal to 10 cm /Vs (T 30 mK) at the barrier thickness 2.0-3.5 nm.] But values 5 10 -10 cm /Vs that are obtained for 6-8 nm thick square p-QWs [32], [33] are also satisfactory for considered diode structures.…”