Extremely Slow Charge Fluctuations in the Metallic State of the Two-Dimensional Molecular Conductor θ−(BEDT−TTF)2RbZn(SCN)4

Abstract

Large charge disproportionation has been confirmed in the metallic state of a $1/4$-filled organic conductor $\theta \mathrm{\text{−}}(\mathrm{B}\mathrm{E}\mathrm{D}\mathrm{T}\mathrm{\text{−}}\mathrm{T}\mathrm{T}\mathrm{F}{)}_2\mathrm{R}\mathrm{b}\mathrm{Z}\mathrm{n}(\mathrm{S}\mathrm{C}\mathrm{N}{)}_4$ by means of ${}^{13}\mathrm{C}$-NMR analysis on a selectively ${}^{13}\mathrm{C}$-enriched single crystal sample. By comparing the homogeneous and inhomogeneous linewidths, the temperature dependence of the extremely slow dynamics of charge fluctuations has been determined first. The exotic nature of the metallic state of this salt is discussed.