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Investigation of Quantum Conductance Fluctuation in Mesoscopic Structure of Degenerate Semiconductor

简并半导体介观结构中量子电导涨落的研究

基本信息

批准号：
63460031
负责人：
MURASE Kazuo
金额：
$ 4.35万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

We have made He^3 cryostat (0.4K) with a compact superconducting malenet (8.5T) and investigated the quantum transport of mesoscopic system under low temperatures and high magnetic fields. The following results are obtained.(1) The magnetic depopulation effect of 1-D subbands is observed in the ultrafine narrow wire (the effective width is 170nm) of GaAs/AlGaAs heterostructures.(2) The unsymmetrical conductance fluctuations under a magnetic field inversion due to the non-local conductivity effect is observed in the small cross wire of GaAs/AlGaAs heterostructure.(3) In the ballistic transport region of quantum wire, where the sample size and the elastic scattering length are comparable, we observed the necative bend resistance, the non-local voltage fluctuations and the overshootine, effect of magnetoresistance near zero field.(4) In the multi-terminal quantum wire, we observed the Shubnikov-de Haas (SdH.) effect in the non-local geometry, where the current probes and voltace probes are separated. The decay lengths of amplitudes in the S.dH. oscillation and the negative bend resistance with respect to the separation distance are measured. The decay length of the negative bend resistance is approximately same to the elastic scattering length of electron, however, that of SdH. oscillation is much longer than the scattering length and it becomes shorter with higher magnetic fields.(5) The Anderson localization of Sb film is observed.(6) The magneto-resistance flutuation is investigated in the ultra-fine narrow wire of Bi. When the length of wire(L) is shorter than the coherence length electron the conductance fluctuations are not universal and will diverse as L^<-2>.

我们用紧凑的超导锰网（8.5T）制作了He^3低温恒温器（0.4K），并研究了介观体系在低温和强磁场下的量子输运。得到如下结果：(1)在GaAs/AlGaAs异质结构的超细窄线（有效宽度为170nm）中观察到1- d亚带的磁性去种群效应。(2)在GaAs/AlGaAs异质结构的小交叉线中，由于非局域电导率效应，在磁场反转下出现了不对称的电导波动。(3)在量子线的弹道输运区，在样品大小和弹性散射长度相当的情况下，我们观察到负弯曲电阻、非局域电压波动和近零场磁电阻的超冲效应。(4)在多端量子线中，我们观察到电流探针和电压探针分离的非局域几何中的舒布尼科夫-德哈斯（SdH.）效应。振幅在sdh中的衰减长度。测量了相对于分离距离的振荡和负弯曲阻力。负弯曲电阻的衰减长度与电子的弹性散射长度大致相同，但与SdH的衰减长度大致相同。振荡比散射长得多，且随磁场的增大而变短。(5)观察到Sb膜的安德森定位。(6)研究了Bi超细窄丝的磁阻波动。当导线长度(L)小于电子的相干长度时，电导波动不具有普适性，其变化规律为L^<-2>。