A shift of the mobility edge at weak magnetic fields

Abstract

We report on magnetoconductivity measurements performed on In₂O_3−x samples near the Anderson transition. The presence of Coulomb correlations severely limits the range of temperatures and fields over which one can meaningfully compare data with theory. By restricting the analysis to data taken at low fields (where the Hall coefficient is constant), the accuracy of the extrapolated value of σ(0) is somewhat compromised. Nevertheless, it is shown that Δσ (0,H) ∼Ce²/h;l₂ with C∼0·045 ± 0·02 in agreement with the theoretical arguments due to Mott and Kaveh (1985) and Shapiro (1984). This value of C is essentially independent of the disorder up to ∼10% of the critical value. Thus, our results imply that, at weak fields, the critical index does not differ from its zero-field value.