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We examine the effect of an in-plane magnetic field on the resistance of a 2-dimensional electron system confined in a silicon quantum well when the Fermi energy is tuned through the upper valley-subband edge while the electrons are otherwise valley-polarized. In contrast to previous experiments on valley-degenerate systems which only showed positive magnetoresistance, when the Fermi energy is at or near the upper valley-subband edge, the magnetoresistance is found to show a distinct negative contribution which is interpreted as being due to spin polarization of the upper valley-subband. [ABSTRACT FROM AUTHOR]

We report a non-monotonic and strongly temperature dependent magneto-resistance observed in clean quantum point contacts. At the same time the conductance of the point contact varies linearly with temperature. This unexpected behavior may be related to electron-electron interactions. [ABSTRACT FROM AUTHOR]

We report the first observation of the metal–insulator transition (MIT) in a two-dimensional electron gas (2DEG) in a Si/SiGe heterostructure at zero field. We have performed an analysis of the temperature dependence of conductivity and magnetoresistance of our sample on the metallic side of the transition using recent theories. [Copyright &y& Elsevier]

An experimental study of the two-, three-, and four-terminal resistance of a ballistic wire is carried out. The wire is fabricated on the basis of high-mobility 2D electron gas in an AlGaAs/GaAs heterojunction. Different behavior of mesoscopic fluctuations of multiterminal resistances is observed depending on the gate voltage and magnetic field. At B = 0.45 T, the four-terminal resistance drops almost to zero and features resembling a ballistic conductance quantization are observed. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]