Critical behavior of the conductivity of Si:P at the metal-insulator transition under uniaxial stress

We report new measurements of the electrical conductivity σ of the canonical three-dimensional metal-insulator system Si:P under uniaxial stress S. The zero-temperature extrapolation of σ(S, T → 0)˜|S-Sc|^μ shows an unprecedently sharp onset of finite conductivity at Sc with an exponent μ = 1. The value of μ differs significantly from that of earlier stress-tuning results. Our data show dynamic σ(S, T) scaling on both metallic and insulating sides, viz. σ(S, T) = σ_c(T)F'(|S - S_c|/T^y) where σ_c(T) is the conductivity at the critical stress S_c. We find y = 1/zv = 0.34 where v is the correlation-length exponent and z the dynamic critical exponent. 1999