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1.
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
2.
A. Urbina C. Díaz-Paniagua A.F. Braña F. Batallán 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):463-468
We present measurements of the diagonal Rxx and off-diagonal Rxy magnetoresistance under quantum Hall conditions on several high electron mobility transistors (HEMT) based on InxGa1-xAs quantum wells. From the magnetoresistance tensor we obtain the longitudinal conductivity σ
xx
. We study the transport mechanisms near the σ
xx
minima at temperatures ranging between 2 K and 35 K; activated transport is the dominant mechanism for temperatures above
7 K while variable range hopping conductivity is significant for lower temperatures. We show that electron-electron correlations
should be taken into account to explain the conductivity vs temperature behaviour below 5 K. Finally, we study the behaviour of the localization length as a function of Landau level
filling and obtain a critical exponent γ = 3.45±0.15.
Received 6 June 2001 and Received in final form 16 October 2001 相似文献
3.
A. E. Kar’kin D. A. Shulyatev A. A. Arsenov V. A. Cherepanov E. A. Filonova 《Journal of Experimental and Theoretical Physics》1999,89(2):358-365
A comparative study of the longitudinal ρ
xx
and transverse ρ
xy
resistivities and magnetic susceptibility χ
ac of La0.8Sr0.2MnO3 single crystals and ceramic samples has been conducted in a wide range of temperatures T=1.7–370 K and magnetic fields, H=0–13.6 T. It turned out that the relation ρ
xy
∼ρ
xx
, which is expected to hold in the case of carrier scattering by magnetic fluctuations, applies to the single crystals. In
polycrystals, an additional H-dependent contribution to the resistivity tentatively attributed to plane (near grain boundaries) and bulk “defects” of the
magnetic sublattice has been detected. The scattering of carriers by these defects does not make a notable contribution to
the anomalous Hall effect and magnetic susceptibility χ
ac. As a result, the curve of ρ
xy
versus ρ
xx
seems to be steeper than a linear dependence. Under the assumption that the materials under investigation are metals with
constant carrier concentrations, the conductivity σ=1/ρ
xx
due to the critical magnetic scattering calculated in the molecular field approximation reproduces the main features of experimental
data, namely, the drop in the amplitude and shift of the resistivity peak near the Curie point with increasing magnetic field
H and also a relatively slow change in the derivative dσ/dH with increasing temperature in the region T⩽T
C
. The large hole concentration of about two per unit cell derived from Hall measurements indicates that carriers of opposite
signs can coexist in these materials.
Zh. éksp. Teor. Fiz. 116, 671–683 (August 1999) 相似文献
4.
The quantum Hall effect structure in the transverse magnetoresistance R
xx
and the Hall resistance R
xy
of heavily doped GaAs layers with a three-dimensional spectrum of the charge carriers is investigated for different field
orientations. The characteristic structures (minima in R
xx
and plateaus in R
xy
) shift much more slowly to higher fields and are suppressed much more rapidly in comparison with the expected angular dependence
for a two-dimensional system. The results are discussed in terms of the anisotropic change of the three-dimensional conductivity
tensor with magnetic field rotation.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 4, 305–308 (25 August 1998) 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.
Two metastable states of a multilayer Ge/p-Ge1−x
Six heterosystem with wide (∼ 35 nm) potential wells (Ge) are observed in strong magnetic fields B at low temperatures. In the first state, the Hall resistivity exhibits an inflection near the value ρxy=h/e
2 scaled to one Ge layer. The longitudinal magnetoresistivity ρxx(B) possesses a minimum in the range of fields where this inflection occurs. The temperature evolution of the inflection in
ρxy(B), the minimum of ρ xx(B), and the value of ρxy at the inflection indicates a weakly expressed state of the quantum Hall effect with a uniform current distribution over
the layers. In the second metastable state, an unusually wide plateau near h/2e
2 with a very weak field dependence is observed in ρxy(B). Estimates show that in these samples the Fermi level lies below but close to the top of the inflection in the bottom of
the well. For this reason, the second state can be explained by separation of a hole gas in the Ge layers into two sublayers,
and the saturation of ρxy(B) near h/2e
2 can be explained by the formation of a quantum Hall insulator state.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 290–297 (25 August 1999) 相似文献
7.
W. Zhong W. Chen H.Y. Jiang X.S. Liu C.T. Au Y.W. Du 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):331-337
Polycrystalline two-layered perovskite La2.5-xK0.5+xMn2O
7 + δ
(0 <
x
< 0.5) samples have been prepared by a modified sol-gel method and their magnetoresistance and magnetocaloric effects have been
studied. A large deviation between the metal-insulator (MI) transition temperature (T
ρ
) and the magnetic transition temperature (TC) is observed. Large magnetoresistance (MR) effects with Δρ/ρ
of ∼40% at 12 kOe are obtained in wide temperature ranges. The maximum of the magnetic entropy change peaks at its Curie temperature
(TC), far above its MI transition temperature (T
ρ
). The large magnetic entropy change (∼1.4 J/kg.K) is obtained in the sample La2.5-xK0.5+xMn2O
7 + δ
(x
= 0.35) upon 10 kOe applied magnetic field.
Received 2 May 2002 / Received in final form 1st October 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: wzhong@ufp.nju.edu.cn 相似文献
8.
D. Yu. Ivanov S. V. Morozov Yu. V. Dubrovskii S. Yu. Shapoval V. V. Valyaev V. L. Gurtovoi 《JETP Letters》1997,66(11):737-741
The Hall mobility of electrons is investigated as a function of the population of size-quantization subbands in the two-dimensional
electron gas of a δ-doped layer in GaAs with constant total electron density N
s
=3.2×1012 cm−2 (three initially filled subbands) at T=4.2 K. The population of the subbands is varied by diamagnetic “ejection” of size-quantization levels (i.e., pushing them
over the Fermi level) by a magnetic field oriented parallel to the plane of the δ-doped layer. The measurements are made in magnetic fields making small angles (5°) with the plane of the doping. The magnetic
field component normal to the plane was used to measure the Hall mobility and density. It is found that the measured Hall
mobility as a function of the ejecting magnetic field has a distinct maximum. This maximum is due to an increase in the electron
mobility in the first subband (the ground subband is assigned the index 0) and electron redistribution between subbands with
in increasing ejecting magnetic field parallel to the plane of the δ layer.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 11, 704–708 (10 December 1997) 相似文献
9.
M. Takigawa M. Ichioka K. Machida 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):303-311
Thermal conductivity κ
xx(T) under a field is investigated in d
x2 - y2-wave superconductors and isotropic s-wave superconductors by the linear response theory, using a microscopic wave function of the vortex lattice states. To study
the origin of the different field dependence of κxx(T) between higher and lower temperature regions, we analyze the spatially-resolved thermal conductivity around a vortex at
each temperature, which is related to the spectrum of the local density of states. We also discuss the electric conductivity
in the same formulation for a comparison.
Received 8 December 2001 and Received in final form 20 March 2002 Published online 6 June 2002 相似文献
10.
A theoretical framework for treating the effects of magnetic fieldH on the pairing theory of superconductivity is considered, where the field is taken in an arbitrary direction with respect
to crystal axes. This is applicable to closed, as well as open normal state Fermi surface (FS), including simple layered metals.
The orbital effects of the magnetic field are treated semiclassically while retaining the full anisotropic paramagnetic contribution.
Explicit calculations are presented in the limits |H| → |H
c2(T)|,T ∼ 0 andT →T
c(|H|), |H| ∼ 0. Effects of weak nonmagnetic impurity scattering, without vertex corrections, have also been taken into account in a
phenomenological way. The final results for the case of open FS and layered materials are found to differ considerably from
those of the closed FS. For example, an important parameter,h(T=0)=|Hc2(0)|/[-Tδ|H
c2
T|δT]T{s0} for the case of a FS open ink
z-direction with thek
z-bandwidth, 4t
3, very small compared to the Fermi energy,E
F, is close to 0.5906, compared to 0.7273 for the closed FS, in the clean limit. Analytical results are given for the magnetic
field dependence ofT
c and the temperature dependence of H
c2 for a model of layered superconductors with widely open FS. For a set of band structure parameters for YBa2Cu3O7 used elsewhere, we find reasonable values for the upper critical fieldH
c2(0), the slope (dH
c2/dT)T
c0, anisotropic coherence lengths ζi(T=0),i=x, y, z, and (dT
c/d|H|)|H| → 0. 相似文献
11.
Temperature (T) dependence on Hall conductivity (σxy) in Si MOS inversion layers measured in 15 T at T=1.4?10 K is investigated by comparing dσxy/dNs, Ns electron concentration, to the calculation based on an effective mobility edge (Ec) model. Temperature dependence of inelastic scattering time is discussed in connection to the T-dependence of Ec. 相似文献
12.
I.L. Drichko I.Yu. Smirnov A.V. Suslov O.A. Mironov D.R. Leadley 《Annalen der Physik》2009,18(12):939-943
We report the results of an experimental study of the magnetoresistance ρxx and ρxy in two samples of p‐Si/SiGe with low carrier concentrations p = 8.2 × 1010 cm‐2 and p = 2 × 1011 cm‐2. The research was performed in the temperature range of 0.3–2 K and in the magnetic fields of up to 18 T, parallel or tilted with respect to the two‐dimensional (2D) channel plane. The large in‐plane magnetoresistance can be explained by the influence of the in‐plane magnetic field on the orbital motion of the charge carriers in the quasi‐2D system. The measurements of ρxx and ρxy in the tilted magnetic field showed that the anomaly in ρxx, observed at filling factor ν = 3/2 is practically nonexistent in the conductivity σxx. The anomaly in σxx at ν = 2 might be explained by overlapping of the levels with different spins 0 ↑ and 1 ↓ when the tilt angle of the applied magnetic field is changed. The dependence of g‐factor g*(Θ)/g*(00) on the tilt angle Θ was determined. 相似文献
13.
Yu. G. Arapov S. V. Gudina A. S. Klepikova V. N. Neverov S. G. Novokshonov G. I. Kharus N. G. Shelushinina M. V. Yakunin 《Journal of Experimental and Theoretical Physics》2013,117(1):144-152
The longitudinal ρ xx (B) and Hall ρ xy (B) magnetoresistances are investigated experimentally in the integer quantum Hall effect (QHE) regime in n-InGaAs/GaAs double quantum well nanostructures in the range of magnetic fields B = (0–16) T and temperatures T = (0.05–70) K before and after IR illumination. The results are evaluated within the scaling hypothesis with regard to electron-electron interaction. 相似文献
14.
In the fractional quantum Hall effect regime, the diagonal (ρxx) and Hall (ρxy) magnetoresistivity tensor components of the two-dimensional electron system (2DES) in gated GaAs/AlxGa1−x
As heterojunctions are measured together with the capacitance between 2DES and the gate. The 1/3-and 2/3-fractional quantum
Hall effects are observed at rather low magnetic fields where the corresponding fractional minima in the thermodynamic density
of the states have already disappeared, thus, implying the suppression of the quasiparticle energy gaps.
The text was submitted by the authors in English. 相似文献
15.
V. A. Kul’bachinskii A. Yu. Kaminskii N. Miyajima M. Sasaki H. Negishi M. Inoue H. Kadomatsu 《JETP Letters》1999,70(11):767-771
The quantization of the Hall resistivity ρxy in the form of plateaus in the dependence of ρxy on the magnetic field B is observed in the semiconductors Bi2Te3 and Sb2Te3; the minima of the transverse magnetoresistivity ρxx correspond to the start of the plateaus. The quantization of ρxy is due to the presence of a current-carrier reservoir. An impurity band with a high density of states or a different band
with a much higher current-carrier effective mass serves as the reservoir.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 11, 754–758 (10 December 1999) 相似文献
16.
G. I. Harus A. N. Ignatenkov N. K. Lerinman A. I. Ponomarev L. D. Sabirzyanova N. G. Shelushinina N. A. Babushkina L. M. Belova 《JETP Letters》1996,64(6):444-449
The temperature and magnetic-field dependences of the resistivity ρ and Hall effect R(j‖ab, B‖c) in a Nd1.82Ce0.18CuO4−δ
single crystal film (T
c
=6 K) is investigated at temperatures 1.4≤T≤20 K and magnetic fields 0≤B≤5.5 T. At the lowest temperature T=1.4 K the resistive state (exhibiting resistivity and the Hall effect) arises in a magnetic field B=0.5 T. A transition to the normal state is completed at B
c
2≃3 T, where the Hall coefficient becomes nearly constant. The negative magnetoresistance due to the weak-localization effect
in the normal state is observed for B>3 T. The nonmonotonic behavior and the inversion of the sign of R(B) in the mixed state are explained in a reasonable way by the flux-flow model with the effect of pinning taken into account.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 6, 407–411 (25 September 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
17.
R. Menegotto Costa L. Mendon?a Ferreira V. N. Vieira P. Pureur J. Schaf 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):107-113
We have studied experimentally the electrical magneto-conductivity near the
superconducting transition of YBa2Cu3O7-δ, YBa2
(Cu2.95Zn0.05)O7-δ and Y(Ba1.75Sr0.25)Cu3O7-δ polycrystalline samples. The measurements were performed in magnetic fields ranging from 0 to 400 Oe applied parallel to
the current orientation. The results show that the resistive transition of these systems proceeds in two stages. The pairing
transition occurs at the bulk critical temperature Tc, where superconductivity is stabilized within small and homogeneous regions of the
sample generically called grains. The regime of approach to the zero resistance state reveals the occurrence of a coherence
transition at a lower temperature Tc0. This transition is related to the connective nature of the granular samples and is controlled by fluctuations of the
order-parameter phase of individual grains. Our experiments show that the Zn-doping, besides depressing the pairing critical
temperature, strongly enlarges the temperature range dominated by effects related to the coherence transition. The substitution
of Ba by Sr causes only a small reduction of Tc, but also enhances significantly the effects related to the grain
coupling phenomenology. In general, our results indicate that these impurity substitutions in YBa2Cu3O7-δ produce or magnify the granularity at a microscopic level, enhancing the effects of phase fluctuations in the conductivity
near the transition. 相似文献
18.
The weak-field Hall voltage in Si-MOS structures with different mobility is studied on both sides of the metal-insulator transition.
In the vicinity of the critical density on the metallic side of the transition, the Hall voltage is found to deviate by 6–20
% from its classical value. The deviation does not correlate with the strong temperature dependence of the diagonal resistivity
ρ
xx
(T). In particular, the smallest deviation in R
xy
is found in the highest-mobility sample, which exhibits the largest variation in the diagonal resistivity ρ
xx
with temperature.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 1, 48–52 (10 July 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
19.
M.Ya. Azbel 《Solid State Communications》1985,54(2):127-130
Experiments yielded rapid rise in the Hall grxy and magnetoresistance ρxx, ρzz in Hg0.76Cd0.24Te to almost linear dependence in strong magnetic fields. This paper relates it to the states, which are extended at the Hall edge for ρxy and between the Hall edges for ρxx, ρzz, while bulk states are localized. Theory agrees with experiments, and suggests that thin enough samples may have zero magnetoresistance in strong enough magnetic fields. 相似文献
20.
Nai-Yi Cui 《Solid State Communications》2004,130(10):663-667
This paper generalises the theorem already obtained [Solid State Commun. 127 (2003) 505] for the high mobility, dissipationless, integer quantum Hall systems at T=0 K to the T>0 K situations. The results obtained are again suitable at both microscopic and macroscopic scales. In comparison [Solid State Commun. 127 (2003) 505], this generalised form gives a universal explicit expression for the Hall conductance σxy(μ,T) between any two points selected in such a system as a function of chemical potential and temperature. Further, thermal deviation Δσxy(μ,T) from the exact quantised values of σxy(μ,T) and the minimum slopes of Hall plateaux in the T>0 cases, observed already in experiments, are also derived in theory. Similar to those in the T=0 K case [Solid State Commun. 127 (2003) 505], the overall quantum Hall behaviour of the system can again be obtained from this theory by simply selecting two points on the two Hall contacts. 相似文献