Nonlinear electric field effects at a continuous Mott-Hubbard transition

We characterize the non-Ohmic portion of the conductivity at temperatures T < 1 K in the highly correlated transition metal chalcogenide Ni(S, Se)(2). Pressure tuning of the T = 0 metal-insulator transition reveals the influe nce of the quantum critical point and permits a direct determination of the dynamical critical exponent z = 2.7(-0.4)(+0.3) Within the framework of fi nite temperature scaling, we find that the spatial correlation length expon ent v and the conductivity exponent gamma differ.