arXiv subjects

E. A. Uskova

Publications and source records attributed to E. A. Uskova.

4 recordsLinked to original sources

arXiv2005

Transport properties of 2D-electron gas in a n-InGaAs/GaAs DQW in a vicinity of low magnetic-field-induced Hall insulator--quantum Hall liquid transition

The resistivity (R) of low mobility dilute 2D-electron gas in a n-InGaAs/GaAs double quantum well (DQW) exhibits the monotonic 'insulating-like' temperature dependence (dR/dT < 0) at T = 1.8 -- 70K in zero magnetic field. This temperature interval corresponds to a ballistic regime (kTtau/hbar > 0.1 -- 3.5) for our samples, and the electron density is on a 'insulating' side of the so-called B = 0 2D metal--insulator transition. We show that the observed localization and Landau quantization is due to the Sigma_xy(T)anomalous T-dependence.

cond-mat.mes-hall↗

arXiv2003

Parallel magnetic field induced magnetoresistance peculiarities of the double quantum well filled with electrons or holes

In In_xGa_{1-x}As/n-GaAs double quantum wells (DQWs) containing an electron gas, the magnetoresistance (MR) peculiarities under parallel magnetic fields caused by the passing of the tunnel gap edges through the Fermi level are revealed. Peculiarities positioned in high fields (~30 T) can only be explained if the spin-splitting of the In_xGa_{1-x}As conduction band is considered, that was neglected in the GaAs/AlGaAs heterostructures, for which solely the effects of this nature have been observed so far. In Ge/p-Ge_{1-x}Si_x DQWs containing a hole gas, local MR peculiarities under parallel fields are discovered as well. But the tunnel gap in these DQWs is too narrow to be responsible for these observations. We suppose, they are due to a complicated shape of the hole confinement subbands.

cond-mat.mes-hall↗

arXiv2001

Quantum corrections to conductivity: from weak to strong localization

Results of detailed investigations of the conductivity and Hall effect in gated single quantum well GaAs/InGaAs/GaAs heterostructures with two-dimensional electron gas are presented. A successive analysis of the data has shown that the conductivity is diffusive for $k_F l=25-2$ and behaves like diffusive one for $k_F l=2-0.5$ down to the temperature T=0.4 K. It has been therewith found that the quantum corrections are not small at low temperature when $k_F l\simeq 1$. They are close in magnitude to the Drude conductivity so that the conductivity $σ$ becomes significantly less than $e^{2}/h$ (the minimal $σ$ value achieved in our experiment is about $3\times 10^{-8}Ω^{-1}$ at $k_Fl\simeq 0.5$ and $T=0.46$ K). We conclude that the temperature and magnetic field dependences of conductivity in whole $k_Fl$ range are due to changes of quantum corrections.

cond-mat.dis-nn↗

arXiv2001

Role of doped layers in dephasing of 2D electrons in quantum well structures

The temperature and gate voltage dependences of the phase breaking time are studied experimentally in GaAs/InGaAs heterostructures with single quantum well. It is shown that appearance of states at the Fermi energy in the doped layers leads to a significant decrease of the phase breaking time of the carriers in quantum well and to saturation of the phase breaking time at low temperature.

cond-mat.soft↗