Magnetoconductance due to parallel magnetic fields in silicon inversion layers.

Abstract

A new anomalous magnetoconductance in parallel magnetic fields has been observed in a two-dimensional electron system formed in n-channel silicon field-effect transistors in fields up to 1.5 T and in a temperature range 1--4.2 K. The magnetoconductance is positive at electron concentrations ${N}_{S}$g2\ifmmode\times\else\texttimes\fi{}${10}^{16}$ electrons/${\mathrm{m}}^{2}$ and has been interpreted as an effect of suppression of the weak-localization correction to the conductivity. The experiment deduces the presence of an electron random walk in the direction perpendicular to the Si-${\mathrm{SiO}}_{2}$ interface with the rms value \ensuremath{\delta}z\ensuremath{\le}2.1\ifmmode\pm\else\textpm\fi{}0.15 A\r{}. At lower electron densities the magnetoconductance changes sign and has a magnitude much larger than predicted by the current electron-electron interaction theory. The enhancement has been explained by including the spin fluctuations induced by disorder.