108 research outputs found
Weak localization in macroscopically inhomogeneous two-dimensional systems: a simulation approach
A weak-localization effect has been studied in macroscopically inhomogeneous
2D system. It is shown, that although the real phase breaking length tends to
infinity when the temperature tends to zero, such a system can reveal a
saturated behavior of the temperature dependence of that parameter, which is
obtained from the standard analysis of the negative magnetoresistance and
usually identified by experimentalists with the phase braking length.Comment: 5 pages, 4 figure
Interference quantum correction to conductivity of Al xGa 1-xAs/GaAs double quantum well heterostructures near the balance
We present the results of experimental investigations of the interference quantum correction to the conductivity of the gated double quantum well Al xGa 1-xAs/GaAs/Al xGa 1-xAs heterostructures. Analyzing the positive magnetoconductiv-ity we obtain the interwell transition rate and the phase relaxation rate under the conditions when one and two quantum wells are occupied. It has been found that the interwell transition rate resonantly depends on the difference between the electron densities in the wells in accordance with the theoretical estimate. The central point, however, is that the dephasing rate in the lower quantum well is independent of whether the upper quantum well contributes to the conductivity or not. The results obtained are interpreted within framework of the recent theory for the dephasing and electron-electron interaction in the double well structures [Burmistrov I S, Gornyi I V and Tikhonov K S 2011 Phys. Rev. B 84 075338]
Spin-orbit splitting of valence and conduction bands in HgTe quantum wells near the Dirac point
Energy spectra both of the conduction and valence bands of the HgTe quantum
wells with a width close to the Dirac point were studied experimentally.
Simultaneous analysis of the Shubnikov-de Haas oscillations and Hall effect
over a wide range of electron and hole densities gives surprising result: the
top of the valence band is strongly split by spin-orbit interaction while the
splitting of the conduction band is absent, within experimental accuracy.
Astonishingly, but such a ratio of the splitting values is observed as for
structures with normal spectrum so for structures with inverted one. These
results do not consistent with the results of kP calculations, in which the
smooth electric filed across the quantum well is only reckoned in. It is shown
that taking into account the asymmetry of the quantum well interfaces within a
tight-binding method gives reasonable agreement with the experimental data.Comment: 10 pages, 16 figure
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