Quantum fluctuations and the closing of the Coulomb gap in a correlated insulator

Abstract

The "switchable mirror" yttrium hydride is one of the few strongly correlated systems with a continuous Mott-Hubbard metal-insulator transition. We systematically map out the low temperature electrical transport from deep in the insulator to the quantum critical point using persistent photoconductivity as a drive parameter. Both activated hopping over a Coulomb gap and power-law quantum fluctuations must be included to describe the data. Collapse of the data onto a universal curve within a dynamical scaling framework (with corrections) requires zν=6.0±0.5, where ν and z are the static and dynamical critical exponents, respectively.

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