arXiv subjects

V. D. Kagan

Publications and source records attributed to V. D. Kagan.

3 recordsLinked 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

Heating of a two-dimensional electron gas by the electric field of a surface acoustic wave

The heating of a two-dimensional electron gas by an rf electric field generated by a surface acoustic wave, which can be described by an electron temperature $T_e$, has been investigated. It is shown that the energy balance of the electron gas is determined by electron scattering by the piezoelectric potential of the acoustic phonons with $T_e$ determined from measurements at frequencies $f$= 30 and 150 MHz. The experimental curves of the energy loss $Q$ versus $T_e$ at different SAW frequencies depend on the value of $ω\barτ_ε$, compared to 1, where $ \bar τ_ε$ is the relaxation time of the average electron energy. Theoretical calculations of the heating of a two-dimensional electron gas by the electric field of the surface acoustic wave are presented for the case of thermal electrons ($ΔT \ll T$). The calculations show that for the same energy losses $Q$ the degree of heating of the two-dimensional electrons (i.e., the ratio $T_e/T$) for $ω\barτ_ε>1$ ($f$= 150 MHz) is less than for $ω\barτ_ε<1$ ($f$=30 MHz). Experimental results confirming this calculation are presented.

cond-mat.mes-hall↗

arXiv1997

The nonlinear effects in 2DEG conductivity investigation by an acoustic method

The parameters of two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure were determined by an acoustical (contactless) method in the delocalized electrons region ($B\le$2.5T). Nonlinear effects in Surface Acoustic Wave (SAW) absorption by 2DEG are determined by the electron heating in the electric field of SAW, which may be described in terms of electron temperature $T_e$. The energy relaxation time $τ_ε$ is determined by the scattering at piezoelectric potential of acoustic phonons with strong screening. At different SAW frequencies the heating depends on the relationship between $ωτ_ε$ and 1 and is determined either by the instantaneously changing wave field ($ωτ_ε$$<1$), or by the average wave power ($ωτ_ε$$>1$).

cond-mat.mes-hall↗