Quantum corrections to the conductance of AlGaAs/GaAs-based quasiballistic quantum wires

Quantum conductance corrections (QCCs) due to weak localization and interaction effects of quantum quasiballistic wires are investigated for the first time. At temperatures in the range 2 K < T < 12 K a crossover of these corrections from one-dimensional behavior to zero-dimensional behavior is observed. It is shown that the phase coherence length in the wires studied is less than the length L-T = ((h) over bar D/kT)(1/2) at all temperatures. It is found that the conventional theory of QCCs describes correctly the experimental temperature dependence of the QCCs but gives a much lower value than the experimental one. (C) 1998 American Institute of Physics.X111sciescopu

Quantum transport in ultrathin CoSi2 polycrystalline films

Quantum transport in ultrathin CoSi2 polycrystalline films was studied for the first time. The temperature corrections to the conductivity of these films and their anomalous magnetoresistance have been observed and investigated. It is shown that they are determined by the effects of interaction and weak localization with the strong spin-orbit and spin scattering taken into account. Unlike the epitaxial crystalline films reported previously our films including one with the thickness larger than 10 nm show no superconductivity down to the lowest temperature (0.2 K). In the thinnest film we used an unusual dimensional crossover from one dimensional behavior of quantum corrections to two dimensional have been observed with lowering temperature, supposedly due to changes of the characteristic correlation length in the sample, which consisted of meandrous conducting paths caused by the presence of pin-holes. (C) 1997 Published by Elsevier Science Ltd.X11sciescopu

Quantum ratchet effects induced by terahertz radiation in GaN-based two-dimensional structures

Photogalvanic effects are observed and investigated in wurtzite (0001)-oriented GaN/AlGaN low-dimensional structures excited by terahertz radiation. The structures are shown to represent linear quantum ratchets. Experimental and theoretical analysis exhibits that the observed photocurrents are related to the lack of an inversion center in the GaN-based heterojunctions.</p

Circular photogalvanic effect in HgTe/CdHgTe quantum well structures

We describe the observation of the circular and linear photogalvanic effects in HgTe/CdHgTe quantum wells. The interband absorption of mid-infrared radiation as well as the intrasubband absorption of terahertz (THz) radiation in the QWs structures is shown to cause a dc electric current due to these effects. The photocurrent magnitude and direction varies with the radiation polarization state and crystallographic orientation of the substrate in a simple way that can be understood from a phenomenological theory. The observed dependences of the photocurrent on the radiation wavelength and temperature are discussed