Variation of the Metallic Onset with Magnetic Field in Doped Germanium

Abstract

We demonstrate substantial magnetic-field tuning of the metal-insulator transition in Ge:Sb for H < 20 kOe. From a fit to the conductivity in a series of samples at millikelvin temperatures in different fields to the critical form σ ~ (n/n_c(H) - 1)^μ, we find that μ ≈ 1 independent of H, but that n_c(H) increases more than 25% by H ~ 20 kOe. Moreover, n_c(H) - n_c(0) α H^(1/2), in agreement with a weak-disorder perturbative scaling approach, but in contrast to recent experimental results in Si:As.

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