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1.
The dependence of the differential resistance r
xx
on the dc current density J
dc in a wide GaAs quantum well with two occupied size quantization subbands has been investigated at the temperature T = 4.2 K in the magnetic fields B < 1 T. A peak, whose position is given by the relation 2R
c
eE
H = ħωc/2, where R
c is the cyclotron radius, E
H is the Hall electric field, and ωc is the cyclotron frequency, has been observed in the r
xx
(J
dc) curves at high filling factors. The experimental results are attributed to Zener tunneling of electrons between the Landau
levels of different subbands. 相似文献
2.
The microwave photoresistance of a double GaAs quantum well with two occupied size-quantization sub-bands E
1 and E
2 has been studied at the temperatures T = 1.6–4.2 K in the magnetic fields B < 0.5 T. The microwave photoresistance of such a system has been found to have a maximum amplitude when the maximum of the
magneto-intersubband oscillations with the number k = (E
2 − E
1)ℏωc coincides with the maximum or minimum of the ω/ωc oscillations, where ω is the microwave frequency and ωc is the cyclotron frequency. It has been shown that the resonance photoresistance that appears in the kth maximum of the magneto-intersubband oscillations is determined by the condition ℏω/(E
2 − E
1) = (j ± 0.2)/k, where k and j are positive integers. 相似文献
3.
A. A. Bykov I. V. Marchishin A. K. Bakarov Jing-Qiao Zhang S. A. Vitkalov 《JETP Letters》2007,85(1):63-66
The effect of dc current I dc on the electron transport in a GaAs quantum well with AlAs/GaAs superlattice barriers is studied experimentally at a temperature of 4.2 K in magnetic fields up to 2 T. A sharp increase in resistance R xx is observed in magnetic fields higher than the critical field B c. The value of B c is found to decrease with increasing the current I dc. The phenomenon observed in the experiment is qualitatively explained by the electric breakdown of superlattice barriers under the action of the Hall field. 相似文献
4.
A. A. Bykov 《JETP Letters》2008,88(6):394-397
Differential resistance r xx in a double GaAs quantum well with two occupied size-quantization subbands has been studied at a temperature of 4.2 K in magnetic fields B < 2 T. The oscillations of r xx with a period in the inverse magnetic field determined by the value of a dc bias current I dc have been discovered in the electron system under investigation at high filling factors in the presence of I dc. The amplitude of magneto-intersubband oscillations has been shown to increase in the r xx oscillation maxima, while the oscillation reversal has been observed in the minima. The discovered oscillations have been shown to be due to Zener tunneling of electrons between Landau levels tilted by a Hall electric field. The experimental data are qualitatively explained by the effect of intersubband transitions on the I dc-dependent component of the electron distribution function. 相似文献
5.
S. S. Murzin 《JETP Letters》2010,91(3):155-157
It has been shown that the observation of the transitions between the dielectric phase and the integer-quantum-Hall-effect
phases with the quantized Hall conductivity σ
xy
q ≥ 3e
2/h announced in a number of works is unjustified. In these works, the crossing points of the magnetic-field dependence of the
diagonal resistivity ρ
xx
at different temperatures T and ωcτ = 1 have been misidentified as the critical points of the phase transitions. In fact, these crossing points are due to the
sign change of the derivative dρ
xx
/dT owing to the quantum corrections to the conductivity. Here, ωc = eB/m is the cyclotron frequency, τ is the transport relaxation time, and m is the effective electron mass. 相似文献
6.
M. I. Petrov D. A. Balaev K. A. Shaikhutdinov K. S. Aleksandrov 《Physics of the Solid State》1999,41(6):881-886
Measurements of the temperature dependence of the electrical resistance R(T) below the superconducting transition temperature have been performed at different values of the transport current in HTSC+CuO
composites modeling a network of weak S-I-S Josephson junctions (S—superconductor, I—insulator). It has been shown experimentally that the temperature dependence R(T) at different values of the transport current is adequately described by means of the mechanism of thermally activated phase
slippage developed by Ambegaokar and Halperin for tunnel structures. Within the framework of this model we have numerically
calculated the temperature dependence of the critical current J
c(T) as defined by various criteria. Qualitative agreement obtains between the measured and calculated temperature dependences
J
c(T).
Fiz. Tverd. Tela (St. Petersburg) 41, 969–974 (June 1999) 相似文献
7.
For the first time submillimetric microwaves (λ<1 mm) are used to observe Azbel' Kaner cyclotron resonance in metals. The very high frequency used (typicallyF≅400 GHz) gives a large value ofωτ (typically 500) and therefore very sharp peaks. The fundamental resonance fieldH
c=m
*
cω/e is rather high (typically 200 KG), so subharmonicsH
c/n can be observed at many values ofH in the field region 0–27 KG. If relatively few electrons participate in the resonance and ifω
cτ≧50 (ω
c=eH/m
*
c,τ relaxation time) thenChambers has shown that the line shapes are independent of relaxation time while the fractional linewidthΔH/H varies as l/ωτ. For the belly orbit in pure copper the conditions of Chambers' theory are satisfied forH≧20 KG parallel to [111] axis.m
* is a minimum andτ=1.8×10−10 s. 相似文献
8.
The role of low density upflowing field-aligned electron beams (FEBs) on the growth rate of the electron cyclotron waves at
the frequencies ω
r < Ωe, propagating downward in the direction of the Earth’s magnetic field, has been analysed in the auroral region at ω
e/Ωe < 1 where ω
e is the plasma frequency and Ωe is the gyrofrequency. The FEBs with low to high energy (E
b) but with low temperature (T
‖b) have no effect on these waves. The FEBs with E
b < 1 keV and T
‖b (> 1.5 keV) have been found to have significant effect on the growth rate. Analysis has revealed that it is mainly the T
‖b which inhibits the growth rate (magnitude) and the range of frequency (bandwidth) of the instability mainly in the higher
frequency spectrum. The inhibition in the growth rate and bandwidth increases with increase in T
‖b. The FEBs with less E
b (giving drift velocity) reduce growth rate more than the beams with larger E
b. The inhibition of growth rate increases with the increase in the ratio ω
e/Ωe indicating that the beams are more effective at higher altitudes.
相似文献
9.
Nonlinear magnetotransport of two-dimensional electrons in modulation-doped GaAs/AlAs heterostructures with anisotropic mobility is investigated. The mobility attains its maximum and minimum values in the $\left[ {1\bar 10} \right]$ and [110] directions, respectively. It is found that, upon an increase in the direct electrical current I dc though Hall bars oriented along the [110] direction, the transition of the two-dimensional system to the state with differential resistance r xx ≈ 0 in a magnetic field occurs at a lower value of I dc and is accompanied by a more pronounced “plunge” into the region of negative r xx values as compared to bars oriented along the $\left[ {1\bar 10} \right]$ direction. The results are explained by the impact of mobility on the spectral diffusion of nonequilibrium charge carriers. 相似文献
10.
A new model of electronic vortices in plasma is studied. The model assumes that the profile of the Lagrangian invariant I, equal to the ratio I=Ω/n of the electronic vorticity to the electron density, is given. The proposed approach takes into account the magnetic Debye
scale r
B
≃B/4πen, which leads to breakdown of plasma quasineutrality. It is shown that the Abrikosov singular model cannot be used to describe
electron vortices in plasmas because of the fundamental limitation on the electron vorticity on the axis of a vortex in a
plasma. Analysis of the equations shows that in the model considered for the electronic vorticity, the total magnetic flux
decreases when the size r
0 of the region in which I≠0 becomes less than c/ωpe (ωpe is the electron plasma frequency). For ω
pe
r
0/c≪1, an electronic vortex is formed in which the magnetic flux decreases as r
0
2
and the inertial component predominates in the electronic vorticity. The structure arising as ω
pe
r
0/c⇒0 is a narrow “hole” in the electron density, which can be identified from the spectrum of electromagnetic waves in this
region.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 461–466 (10 April 1998) 相似文献
11.
12.
A Gaussian whistler pulse is shown to cause ponderomotive acceleration of electrons in a plasma when the peak whistler amplitude
exceeds a threshold value and the whistler frequency is greater than half the cyclotron frequency, ω>ω
c
/2. The threshold amplitude decreases with the ratio of plasma frequency to electron cyclotron frequency, ω
p
/ω
c
. However, above the threshold amplitude, the acceleration energy decreases with ω
p
/ω
c
. The electrons gain velocities about twice the group velocity of the whistler. 相似文献
13.
The dielectric properties of the ceramics of (1 − x)BiFeO3 − x(KBi)1/2TiO3 (0.40 < x < 0.85) solid solutions with an orthorhombic structure have been studied using impedance spectroscopy in the frequency range
25–106 Hz at different temperatures. It has been shown that these solid solutions undergo a diffuse ferroelectric phase transition.
The Curie temperature is found to be in the range 620–640 K. The activation energies of dielectric polarization relaxation
(δE
M
) and dc charge carriers (ΔE
dc) are determined. It has been established that, in the vicinity of 460 K, ΔE
dc increases jumpwise as the temperature increases. 相似文献
14.
E. B. Olshanetsky Z. D. Kvon S. S. Kobylkin D. A. Kozlov N. N. Mikhailov S. A. Dvoretskii J. C. Portal 《JETP Letters》2011,93(9):526-529
Magnetotransport of a quasi-three-dimensional (100-nm) HgTe film in quantized magnetic fields has been experimentally investigated.
It has been found that the film exhibits pronounced quantization of the Hall resistance accompanied by deep minima of the
dissipative resistance. A transition from the three-dimensional behavior of Shubnikov-de Haas oscillations in semiclassical
magnetic fields (ωcτ
q
≤ 1) to a two-dimensional one in the quantum-Hall-effect regime has been discovered. The conduction electron cyclotron effective
mass in mercury telluride has been determined from the temperature dependence of the Shubnikov-de Hass oscillations in such
magnetic fields. 相似文献
15.
Malay Bandyopadhyay 《Journal of statistical physics》2010,140(3):603-618
In this work, low temperature thermodynamic behavior in the context of cyclotron motion of a charged-oscillator with different
coupling schemes is analyzed. We find that finite dissipation substitutes the zero-coupling result of exponential decay of
entropy by a power law behavior at low temperature. The power of the power law explicitly depends on the nature of the power
spectrum of the heat bath. It is seen that velocity–velocity coupling is the most advantageous coupling scheme to ensure the
third law of thermodynamics. The cases of confinement (ω
0≠0) and without confinement (ω
0=0) are discussed separately. It is also revealed that different thermodynamic functions are independent of magnetic field
at very low temperature for ω
0≠0, but they depend on cyclotron frequency (ω
c
=eB/mc) for ω
0=0. 相似文献
16.
S. S. Murzin 《JETP Letters》1998,67(3):216-221
The conductance of doped n-GaAs films is studied experimentally as a function of magnetic field and temperature in strong magnetic fields right up to
the quantum limit (ħωc = E
F). The Hall conductance G
xy is virtually independent of temperature T until the transverse conductance G
xx is quite large compared with e
2/h. In strong fields, when G
xx becomes comparable to e
2/h, G
xy starts to depend on T. The difference between the conductances G
xx at the two temperatures 4.2 and 0.35 K depends only weakly on the magnetic field H over a wide range of magnetic fields, while the conductances G
xx themselves vary strongly. The results can be explained by quantum corrections to the conductance as a result of the electron-electron
interaction in the diffusion channel. The possibility of quantization of the Hall conductance as a result of the electron-electron
interaction is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 3, 201–206 (10 February 1998) 相似文献
17.
M. A. Zelikman 《Physics of the Solid State》1997,39(11):1751-1755
A system of pancake vortices formed near the boundary of a sample in a monotonically increasing external magnetic field is
calculated with allowance for pinning due to the cellular structure of the medium for various values of the pinning parameter
I, which is proportional to the critical current of the junction and the cell diameter. The shortest distance from the outermost
vortex to the nearest neighbor is proportional to I
−11. It is shown that the pinning parameter has a critical value I
c separating two regimes with different types of critical states. For I<I
c the external magnetic field has a threshold value H
t(I), above which the field immediately penetrates the interior of the junction to an infinite distance. For I>I
c the magnetic field decays linearly from the boundary into the interior of the junction. The value obtained in the study,
I
c=3.369, differs from the value of 0.9716 postulated by other authors. The dependence of the slope of the magnetic field profile
near the boundary on I is determined. It is shown that the slope is independent of I in intervals 2πk<I<2πk+π.
Fiz. Tverd. Tela (St. Petersburg) 39, 1958–1963 (November 1997) 相似文献
18.
An experimental study is reported of the effect of an electric field E⩽120 MV/m and of temperature T on the critical current I
c and I-V characteristics of yttrium-based high-T
c superconducting ceramics. The materials studied were copper-deficient ceramics, YBa2Cu3−x
Oy (D samples), and YBa2Cu3−x
Oy/Agx ceramics [S samples with silver present in amounts equal to the copper deficiency (0⩽x⩽0.4)]. It has been established that in D samples at 77 K, the electric field increases I
c and reduces substantially R for I>I
c, whereas in S samples no field effect is observed. Measurements of the I
c(T) dependence near the critical temperature showed that they can be described for all samples by a relation of the type I
c
=const(1−T/T
c
)α, where α≈1 for the D samples, and α≈2 for the S samples. The results obtained suggest that the electric-field effect correlates with the existence in the ceramic of SIS-type weak links at grain boundaries.
Fiz. Tverd. Tela (St. Petersburg) 40, 1195–1198 (July 1998) 相似文献
19.
A bi-epitaxial (001)YBa2Cu3O7−δ
/(110)BaZrO3/(001)CeO2 three-layer heterostructure has been grown on (100)SrTiO3 by laser ablation. The epitaxial relations between the layers making up the heterostructure were derived from x-ray diffraction
data. The I
cRn product for the bi-epitaxial Josephson junctions thus obtained was within 1–1.5 mV for 4.2 K, and 30–60 μV for 77 K. The normal resistance R
n=(2–5 Ω) was practically independent of temperature. The magnetic field dependences of I
c had typically a clearly pronounced main maximum, followed by distorted subsequent peaks. Interaction of the Josephson ac
current with self-induced electromagnetic waves at the 45° grain boundary and with external microwave radiation (f=11 GHz) produced current steps in the I-V characteristics of the bi-epitaxial junctions at the corresponding voltages.
Fiz. Tverd. Tela (St. Petersburg) 39, 1732–1738 (October 1997) 相似文献
20.
G. Kh. Panova A. A. Nikonov A. A. Naberezhnov A. V. Fokin 《Physics of the Solid State》2009,51(11):2225-2228
This paper reports on a study of the resistance and differential magnetic susceptibility χ
ac
of lead embedded in nanosized glass pores with a diameter of ∼7 mm, which was performed at temperatures of 6–300 K and magnetic
fields of up to 6 T. The field dependence of the resistance R(H) and the temperature dependences of the real, χ″(T), and imaginary, χ″(T), parts of magnetic susceptibility reveal indications of superconducting phase transitions associated with the volume and
surface superconductivity of Pb nanopar ticles. The measurements of the field dependence of resistance have been used to set
up the H
c
-T
c
phase diagram and to carry out a comparison with the study of the heat capacity performed on the same samples. 相似文献