74 research outputs found
Effect of exchange electron-electron interaction on conductivity of InGaAs single and double quantum wells in ballistic regime
We report an experimental study of quantum conductivity corrections for
two-dimensional electron gas in a GaAs/InGaAs/GaAs single and double quantum
wells in a wide temperature range (1.8-100) K. We perform a comparison of our
experimental data for the longitudinal conductivity at zero magnetic field to
the theory of interaction-induced corrections to th transport coefficients. In
the temperature range from 10 K up to (45-60) K, wich covers the ballistic
interaction regimes for our samples, a rather good agreement between the theory
and our experimental results has been found
Temperature dependence of quantum lifetime in n-InGaAs/GaAs structures with strongly coupled double quantum wells
Longitudinal ρxx(B) and Hall ρxy(B) magnetoresistances are experimentally investigated as a function of in-plane and transverse magnetic fields in n-InGaAs/GaAs nanostructures with strongly-coupled double quantum wells in the temperature range T = 1.8-70 K and magnetic fields B = 0-9.0 T. Experimental data on the temperature dependence of quantum lifetime in diffusive (kBT/τtr ≪ 1) and ballistic (kBT/τtr ≫ 1) regimes are reported. It has been found that in the ballistic regime in the temperature range where kBT/EF < 0.1, the observed quadratic temperature dependence of quantum lifetime is determined by inelastic electron-electron scattering. However, the temperature dependence of quantum lifetime cannot be quantitatively described by the existing theories in the whole temperature range. © 2013 American Institute of Physics
The key role of smooth impurity potential in formation of hole spectrum for p-Ge/Ge_{1-x}Si_x heterostructures in the quantum Hall regime
We have measured the temperature (0.1 <= T <= 15 K) and magnetic field (0 <=
B <= 12 T) dependences of longitudinal and Hall resistivities for the
p-Ge_0.93Si_0.07/Ge multilayers with different Ge layer widths 10 <= d_w <= 38
nm and hole densities p_s = (1-5)10^11 cm^-2. Two models for the long-range
random impurity potential (the model with randomly distributed charged centers
located outside the conducting layer and the model of the system with a spacer)
are used for evaluation of the impurity potential fluctuation characteristics:
the random potential amplitude, nonlinear screening length in vicinity of
integer filling factors nu = 1 and nu = 2 and the background density of state
(DOS). The described models are suitable for explanation of the unusually high
value of DOS at nu = 1 and nu = 2, in contrast to the short-range impurity
potential models. For half-integer filling factors the linear temperature
dependence of the effective QHE plateau-to-plateau transition width nu_0(T) is
observed in contrast to scaling behavior for systems with short-range disorder.
The finite T -> 0 width of QHE transitions may be due to an effective low
temperature screening of smooth random potential owing to Coulomb repulsion of
electrons.Comment: Accepted for publication in Nanotechnolog
Tunneling effects in tilted magnetic fields in n-InGaAs/GaAs structures with strongly coupled double quantum wells
The effects of tunneling between two parallel two-dimensional electron gases in n-InGaAs/GaAs nanostructures with strongly coupled double quantum wells with a change in the in-plane component of a tilted magnetic field (up to Bnorm of matrix = 9.0 T) in the temperature range T = 1.8-70.0 K are investigated. A nonmonotonic temperature dependence of the inverse quantum lifetime τq -(T) is obtained from analysis of the dependence of the longitudinal resistance on the parallel component of the tilted magnetic field at fixed temperatures, ρxx(Bnorm of matrix, T). The quadratic portion of this dependence is found to be due to the contribution of inelastic electron-electron scattering. The decrease in the inverse quantum lifetime τq -(T) at T > 0.1T F cannot be described within known theories; it seems, it is not related to the processes of electron momentum relaxation. © 2013 Pleiades Publishing, Ltd
Parabolic negative magnetoresistance in p-Ge/Ge1-xSix heterostructures
Quantum corrections to the conductivity due to the weak localization (WL) and
the disorder-modified electron-electron interaction (EEI) are investigated for
the high-mobility multilayer p-Ge/Ge1-xSix heterostructures at T = (0.1 -
20.0)K in magnetic field B up to 1.5T. Negative magnetoresistance with
logarithmic dependence on T and linear in B^2 is observed for B >= 0.1T. Such a
behavior is attributed to the interplay of the classical cyclotron motion and
the EEI effect. The Hartree part of the interaction constant is estimated
(F_/sigma = 0.44) and the WL and EEI contributions to the total quantum
correction /Delta /sigma at B = 0 are separated (/Delta /sigma_{WL} ~ 0.3/Delta
/sigma; /Delta /sigma_{EEI} ~ 0.7/Delta /sigma).Comment: 3 pages, 4 figure
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