Magnetic field induced charge redistribution in artificially disordered quantum Hall superlattices

Abstract

The photoluminescence from individual quantum wells of artificially disordered weakly coupled multi-layers embedded in wide AlGaAs parabolic wells was investigated in a strong magnetic field. We show that the response of the individual wells is very different from the average response of the multi-layers studied by transport measurements and that photoluminescence represents a local probe of the quantum Hall state formed in three-dimensional electron system. The observed magnetic field induced variations of the in-layer electron density demonstrate the formation of a new phase in the quasi-three-dimensional electron system. The sudden change in the local electron density found at the Landau filling factor ν = 1 by both the magneto-transport and the magneto-photoluminescence measurements was assigned to the quantum phase transition.

Excitonic spin-splitting in quantum wells with a tilted magnetic field

“…, where the symbols ± E, , ± HH, , and ± LH, indicate the electron, heavy-hole and light-hole spin polarized carriers, respectively. As demonstrated in previously published works [9,10,17], for magnetic fields higher than a critical value (here about 6 T), the MQW response is dominated by electrons residing in the central quantum well. This result supports the use of a single quantum well approach to describe the intentionally disordered MQW system.…”

Spectroscopic evidence of quantum Hall interlayer tunneling gap collapse caused by tilted magnetic field in a GaAs/AlGaAs triple quantum well

“…As demonstrated in Refs. [3,17,20,28,[37][38][39][40][41][42], the electron correlations in MQWs lead to the formation of a collective ground state, like a charge-density wave, which manifests itself in a corresponding redistribution of the electron density over the quantum wells. Such changes in the local electron density may modify the character of the gaps in the range of the magnetic field where the interaction energy is comparable to the Landau-level separation.…”

“…It is worth mentioning that the effects of electron correlations were also observed in a high-mobility weakly coupled MQW embedded in a wide AlGaAs parabolic well where the quantum transition manifesting itself in a redistribution of the electron density over the quantum wells was found in Refs. [19][20][21]. An important result of electron correlations in MQW is the collapse of the QH tunneling gaps, which has been predicted to occur in coupled QH bilayers in tilted magnetic fields B in Ref.…”

Dynamics of photogenerated carriers near magnetic field driven quantum phase transition in aperiodic multiple quantum wells

“…In the presence of free electrons, the strength of the disorder potential is reduced, due to the screening effect. The effective disorder strength was determined as in [8]. The electron con centration and mobilities in the studied here sample with the effective disorder strength δ = 2.3, measured at T = 90 mK, were 3.7 × 10¹¹ cm −2 and 2 × 10 5 cm 2 V −1 s −1 , respectively.…”

“…The observed transition manifested itself in a corre sponding change of the slope of the Hall resistance and it was understood as a kind of quantum phase transition leading to a spatial redistribution of the charge in a multicomponent elec tron system predicted in [4][5][6][7]. The photoluminescence (PL) from individual quantum wells, associated with the confined electron density, was used to probe the distribution of the elec tron density over the MQW in [8]. The obtained results show the magnetic field driven relocation of the electron density from the lateral quantum wells to the central quantum well associated with the formation of a new phase in the MQW electron system.…”