The electron glass in a switchable mirror: relaxation, ageing and universality

The rare earth hydride YH_(3−δ) can be tuned through the metal–insulator transition both by changing δ and by illumination with ultraviolet light. The transition is dominated by strong electron–electron interactions, with transport in the insulator sensitive to both a Coulomb gap and persistent quantum fluctuations. Via a systematic variation of UV illumination time, photon flux, carrier density, and temperature, we demonstrate that polycrystalline YH_(3−δ) serves as a model system for studying the properties of the interacting electron glass. Prominent among its features are logarithmic relaxation, ageing, and universal scaling of the conductivity