Investigation of Quantum Conductance Fluctuation in Mesoscopic Structure of Degenerate Semiconductor

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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>.