Exchange- and correlation-induced charge transfer observed in independently contacted triple-quantum-well structures

Abstract

There have been predictions that for closely spaced two-dimensional electron gases ͑2DEG's͒, charge transfer between the 2DEG's can arise from electron interactions due to exchange and correlation ͓Ruden and Wu, Appl. Phys. Lett. 59, 2165 ͑1991͔͒. In this study, we are able to determine accurately the charge in each of the 2DEG's of a triple-quantum-well structure. The results demonstrate that as the charge in one 2DEG is reduced, by applying a negative gate voltage the adjacent layer can gain charge; thus charge is effectively transferred between the 2DEG's. This type of charge transfer cannot be explained by a simple noninteracting model of the structure, but can be modeled by including intralayer electron interactions in the form of exchange and correlation correction terms within the local-density approximation. The inclusion of these many-body interaction terms into our model leads to a good qualitative agreement with the experimental data, confirming that the origin of the charge transfer is electron interactions.

Exchange instabilities in semiconductor double-quantum-well systems

“…A related issue we investigate connects with the recent experimental search [15][16][17] to observe the predicted charge transfer instability with some of the papers 15 reporting experimental support for an abrupt double-to-single-layer transition in a double quantumwell structure. These experimental studies involve measurements of layer electron densities [via low field Shubnikov-de Haas (SdH) oscillations] in a double quantum well system under the application of an external electric field.…”

“…exchange-correlation) induced exchange instabilities in two dimensional systems. While much of this recent activity [3][4][5][6][7][8][9][10] focuses on the situation in the presence of an external magnetic field, there has also been considerable interest [10][11][12][13][14][15][16][17] in the possibility of exchange instabilities in two dimensional electron gases in the absence of any external magnetic fields. In this paper we theoretically investigate a specific zero magnetic field exchange instability, namely a charge transfer instability, which has been predicted to occur in semiconductor double quantum well systems 10,11,[15][16][17] under suitable conditions.…”

“…These experimental studies involve measurements of layer electron densities [via low field Shubnikov-de Haas (SdH) oscillations] in a double quantum well system under the application of an external electric field. The applied electric field explicitly breaks the layer symmetry in the problem, and the observed nonlinearity [15][16][17] in the layer depopulation is a direct manifestation of the so-called exchange-correlation induced "negative compressibility" effect 18 . We study the layer/subband electron densities in the GaAs double quantum well structures in the presence of an applied electric field within the self-consistent spin-polarized local-density-approximation, obtaining excellent agreement with the existing experimental measurements [15][16][17] .…”

Mode mixing in antiferromagnetically correlated double quantum wells

“…Another feature of these devices of importance to the current work is the ex-tra degree of freedom available when multiple layers are present, as in multiple quantum wells or superlattices. This new degree of freedom allows transitions to states with order not only in the intra-layer electronic degrees of freedom but also in diagonal or off diagonal inter-layer charge [2][3][4][5][6][7][8][9][10][11][12][13] or spin 10,[14][15][16][17][18] observables.…”

Spintronic Spin Accumulation and Thermodynamics

“…The second potential experiment I discuss is a variant on one which has been used in the past [9,10,11,12] to measure the compressibility of two-dimensional electron gas layers. It exploits techniques which have been developed [13] to make separate contact to nearby two-dimensional electron layers.…”