Measurements of low-frequency noise in thick-film resistors at low temperatures are reported. Films were prepared in a standard “high temperature” process: 20 nm sized RuO2 powder was mixed with 0.5 μm granular lead–borosilicate glass and organic solvent to give a paste, which was then screen printed onto alumina substrates and fired in a tunnel furnace. Measurements below liquid helium temperature reveal that the low frequency (1/f) noise increases with decreasing temperature, approximately as T−α, α=2.1±0.1. Up to 4 T no dependence of noise intensity on magnetic field has been observed. Measurements of noise spectra in the range 4−300 K show that spectral and temperature slopes obey Dutta, Dimon, and Horn equation [Phys. Rev. Lett. 43, 646 (1979)] only in the range T>10 K. Below this temperature a gap of constant width opens between noise exponent calculated from the spectral slope and from temperature dependence of noise magnitude. This gap occurs due to the change of noise coupling mechanism that takes place at ≈10 K. At higher temperatures this coupling is temperature independent. At lower temperatures coupling becomes temperature dependent. It is shown that data agree quantitatively with the concept that noise sources modulate energies for thermally activated hops in the percolation network.

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Monte Carlo calculations of shot noise power S in one-and two-dimensional Anderson models of a disordered conductor are presented. For quasi-one-dimensional geometry all theoretical results derived from random matrix theory are confirmed in ballistic-to-diffusive, metallic, and weak localization regimes. For two dimensions in the weak localization regime the relation Sϭ 1 3 Gϩ␦S 2e 2 /h with ␦S ϭ0.123 74 is found. In the ballistic-to-metallic and strongly localized regimes both one-and two-dimensional geometries behave in the same manner.

Abstract. The experimental results obtained for the magneto-transport in the InGaAs/InAlAs double quantum wells (DQW) structures of two different shapes of wells are reported. The beating-effect occurred in the Shubnikov-de Haas (SdH) oscillations was observed for both types of the structures at low temperatures in the parallel transport when magnetic field was perpendicular to the layers. An approach to the calculation of the Landau levels energies for DQW structures was developed and then applied to the analysis and interpretation of the experimental data related to the beating-effect. We also argue that in order to account for the observed magnetotransport phenomena (SdH and Integer Quantum Hall effect), one should introduce two different quasi-Fermi levels characterizing two electron sub-systems regarding symmetry properties of their states, symmetric and anti-symmetric ones which are not mixed by electron-electron interaction. Magnetospectroscopy of symmetric and anti-symmetric states in double quantum wells2