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-S_c|^μ shows an unprecedently sharp onset of finite conductivity at S_c 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/zν = 0.34 where ν is the correlation-length exponent and z the dynamic critical exponent.