arXiv subjects

A. I. Toropov

Publications and source records attributed to A. I. Toropov.

21 records · Page 2Linked to original sources

arXiv1999

High-Frequency Hopping conductivity of Disordered 2D-system in the IQHE Regime

High frequency (hf) conductivity in the form $σ^{hf} = σ_1^{hf} - iσ_2^{hf}$ was obtained from the measurement of Surface Acoustic Waves (SAW) attenuation and velocity (f=30 MHz) in GaAs/AlGaAs heterostructures ($n=1.3-7\cdot 10^{11}cm^{-2}$). It has been shown that in the Integer Quantum Hall Effect (IQHE) regime for all the samples at magnetic fields corresponding to the middle of the Hall plateaus and T=1.5 K, $σ_1 / σ_2 =0.14 \pm 0.03$. The ratio $σ_1 / σ_2=0.15$ points the case when the high-frequency hopping conductivity mechanism (electronic transition between the localized states formed by "tight" pairs) is valid \cite{1}. Dependencies of $σ_1$ and $σ_2$ on temperature and magnetic field is analyzed width of the Landau band broadened by the impurity random potential is determined.

cond-mat.mes-hall↗

arXiv1998

Quantum Hall Effect induced by electron-electron interaction in disordered GaAs layers with 3D spectrum

It is shown that the observed Quantum Hall Effect in epitaxial layers of heavily doped n-type GaAs with thickness (50-140 nm) larger the mean free path of the conduction electrons (15-30 nm) and, therefore, with a three-dimensional single-particle spectrum is induced by the electron-electron interaction. The Hall resistance R_xy of the thinnest sample reveals a wide plateau at small activation energy E_a=0.4 K found in the temperature dependence of the transverse resistance R_xx. The different minima in the transverse conductance G_xx of the different samples show a universal temperature dependence (logarithmic in a large range of rescaled temperatures T/T_0) which is reminiscent of electron-electron-interaction effects in coherent diffusive transport.

cond-mat.mes-hall↗

arXiv1998

2D Lattice of coupled Sinai billiards: metal or insulator at g<<1

We investigate the transport in a two-dimensional (2D) lattice of coupled Sinai billiards fabricated on the basis of a high-mobility 2D electron gas in GaAs/AlGaAs heterojunction. For the states with low reduced conductivity g<<1 an anomalously weak temperature dependence of g was found. The large negative magnetoresistance described by the Lorentz line-shape of the width corresponding to the half magnetic flux quantum through the area of the billiard is observed. In going from g>1 to g<<1 it strongly increases. The Shubnikov-de Haas oscillations and commensurability magnetoresistance peak are preserved at g<<1. The data suggest that the system studied behaves more like a metal than an insulator at g<<1 and is not described by the generally accepted picture of Anderson localization.

cond-mat.mes-hall↗