Critical Behavior of the Conductivity of Si:P at the Metal-Insulator Transition under Uniaxial Stress

TL;DR

This study investigates the critical behavior of electrical conductivity in Si:P near the metal-insulator transition under uniaxial stress, revealing a sharp onset of conductivity and scaling laws with new critical exponents.

Contribution

It provides new measurements of conductivity under uniaxial stress and identifies a sharp transition with a novel critical exponent mu = 1, differing from previous results.

Findings

Sharp onset of finite conductivity at critical stress S_c

Scaling behavior of conductivity with temperature and stress

Critical exponent mu = 1 and dynamical scaling exponent y = 0.34

Abstract

We report new measurements of the electrical conductivity sigma of the canonical three-dimensional metal-insulator system Si:P under uniaxial stress S. The zero-temperature extrapolation of sigma(S,T -> 0) ~\S - S_c\^mu shows an unprecidentedly sharp onset of finite conductivity at S_c with an exponent mu = 1. The value of mu differs significantly from that of earlier stress-tuning results. Our data show dynamical sigma(S,T) scaling on both metallic and insulating sides, viz. sigma(S,T) = sigma_c(T) F(\S - S_cT^y) where sigma_c(T) is the conductivity at the critical stress S_c. We find y = 1/znu = 0.34 where nu is the correlation-length exponent and z the dynamic critical exponent.