Emergence of non-equilibrium charge dynamics in a charge-cluster glass

Non-equilibrium charge dynamics, such as cooling-rate-dependent charge vitrification and physical aging, have been demonstrated for a charge-cluster glass in $\theta$-(BEDT-TTF)${}_2$CsZn(SCN)${}_4$ using electron transport measurements. The temperature evolution of the relaxation time obeys the Arrhenius law, indicating that the glass-forming charge liquid can be classified as a “`strong” liquid in the scheme of canonical structural-glass formers. X-ray diffuse scattering further reveals that the spatial growth of charge clusters in the charge liquid is frozen below the glass transition temperature, indicating an intrinsic relationship between dynamics and structure in the charge-cluster glass.