68 research outputs found
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]
Weak antilocalization in quantum wells in tilted magnetic fields
Weak antilocalization is studied in an InGaAs quantum well. Anomalous
magnetoresistance is measured and described theoretically in fields
perpendicular, tilted and parallel to the quantum well plane. Spin and phase
relaxation times are found as functions of temperature and parallel field. It
is demonstrated that spin dephasing is due to the Dresselhaus spin-orbit
interaction. The values of electron spin splittings and spin relaxation times
are found in the wide range of 2D density. Application of in-plane field is
shown to destroy weak antilocalization due to competition of Zeeman and
microroughness effects. Their relative contributions are separated, and the
values of the in-plane electron g-factor and characteristic size of interface
imperfections are found.Comment: 8 pages, 8 figure
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
Two-dimensional semimetal in a wide HgTe quantum well: magnetotransport and energy spectrum
The results of experimental study of the magnetoresistivity, the Hall and
Shubnikov-de Haas effects for the heterostructure with HgTe quantum well of
20.2 nm width are reported. The measurements were performed on the gated
samples over the wide range of electron and hole densities including vicinity
of a charge neutrality point. Analyzing the data we conclude that the energy
spectrum is drastically different from that calculated in framework of
-model. So, the hole effective mass is equal to approximately and
practically independent of the quasimomentum () up to cm, while the theory predicts negative (electron-like)
effective mass up to cm. The experimental
effective mass near k=0, where the hole energy spectrum is electron-like, is
close to , whereas the theoretical value is about
Interaction correction to the conductivity of two-dimensional electron gas in InGaAs/InP quantum well structure with strong spin-orbit coupling
The electron-electron interaction quantum correction to the conductivity of
the gated single quantum well InP/InGaAs heterostructures is
investigated experimentally. The analysis of the temperature and magnetic field
dependences of the conductivity tensor allows us to obtain reliably the
diffusion part of the interaction correction for different values of spin
relaxation rate, . The surprising result is that the spin relaxation
processes do not suppress the interaction correction in the triplet channel
and, thus, do not enhance the correction in magnitude contrary to theoretical
expectations even in the case of relatively fast spin relaxation,
.Comment: 7 pages, 6 figure
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