Nonlinear Electric Field Effects at a Continuous Mott-Hubbard Transition

Abstract

We characterize the non-Ohmic portion of the conductivity at temperatures $T<1\phantom{\rule{0ex}{0ex}}\mathrm{K}$ in the highly correlated transition metal chalcogenide $\mathrm{Ni}(\mathrm{S},\mathrm{Se}{)}_{2}$. Pressure tuning of the $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ metal-insulator transition reveals the influence of the quantum critical point and permits a direct determination of the dynamical critical exponent ${z\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.7}_{\ensuremath{-}0.4}^{+0.3}$. Within the framework of finite temperature scaling, we find that the spatial correlation length exponent $\ensuremath{\nu}$ and the conductivity exponent $\ensuremath{\mu}$ differ.