Metal-Insulator Transition in Uncompensated Si:P in the Presence of a Magnetic Field

Abstract

We report on detailed measurements of the electrical conductivity σ(T) in uncompensated Si:P in a magnetic field B of 6 T between 30 mK and 1 K. The approximate relation σ(T) = σ(0) + mB √T allows a reliable extrapolation of σ(0). The critical behaviour σ(0) ∼ (N - Ne)μ' close to the critical P concentration Ne yields a critical exponent μ' ≈ 1.3, with a tendency to smaller values at a crossover concentration which is close to the concentration where mB changes strongly. The implications for the previously proposed solution to the exponent puzzle for B = 0 are discussed.