Dephasing and interwell transitions in double quantum well heterostructures

Abstract

The interference quantum correction to the conductivity in the gated double quantum well AlxGa1−xAs/GaAs/AlxGa1−xAs structures is studied experimentally. The consistent analysis of the interference induced positive magnetoconductivity allows us to find the interwell transition time τ12 and the electron dephasing time τ φ . It has been obtained that τ −1 12 resonantly depends on the difference between the electron densities in the wells as predicted theoretically. The dephasing times have been determined under the conditions when one and both quantum wells are occupied. The surprising result is that the τ φ value in the one well does not depend on the occupation of the other one.

Interaction correction to conductivity of AlxGa1−xAs/GaAs double quantum well heterostructures near the balance

“…Detailed analysis of the gate voltage dependences of the electron densities and mobilities performed for these structures in Ref. 13 demonstrates that near the balance, the mobilities have close values. The magnetic field dependences of σ xx , σ xy , and σ xx,xy = σ xx,xy (4.2 K) − σ xx,xy (1.35 K) taken for the structure 3243 at V g = −1.5 V are presented in Figs.…”

“…Balance is the regime of the equal electron densities in the wells. The energy splitting between the symmetric and antisymmetric states ( SAS ) in this regime is about 0.1 meV, 13 that is much less than 1/τ and less than the temperature under our experimental conditions. For both heterostructures, the results obtained were mostly analogous and in what follows, we shall discuss in more detail the results obtained for the structure 3243.…”

“…An unexpected result has been obtained in Ref. 13. Analyzing the positive magnetoconductivity induced by suppression of the quantum interference by magnetic field, the authors have found that the dephasing rate in the lower quantum well is independent of whether the upper quantum well contributes to the conductivity or not.…”

“…The main parameters of the samples have been determined in Ref. 13 and for two regimes considered in this paper are listed in Table I. The regime when only the lower quantum well is occupied is referred as SQW regime.…”

“…13. The gated samples were made on the basis of the DQW heterostructures in which the two GaAs quantum wells of width 8 nm are separated by 10 nm Al 0.3 Ga 0.7 As barrier.…”