Anion Effects On Electronic Structure And Electrodynamic Properties Of The Mott Insulator Kappa-(Bedt-Ttf)(2)Ag-2(Cn)(3)

The Mott insulator kappa-(BEDT-TTF)(2)Ag-2(CN)(3) forms a highly-frustrated triangular lattice of S = 1/2 dimers with a possible quantum-spin-liquid state. Our experimental and numerical studies reveal the emergence of a slight charge imbalance between crystallographically inequivalent sites, relaxor dielectric response, and hopping dc transport. In a broader perspective we conclude that the universal properties of strongly-correlated charge-transfer salts with spin liquid state are an anion-supported valence band and cyanide-induced quasidegenerate electronic configurations in the relaxed state. The generic low-energy excitations are caused by charged domain walls rather than by fluctuating electric dipoles. They give rise to glassy dynamics characteristic of dimerized Mott insulators, including the sibling compound kappa-(BEDT-TTF)(2)Cu-2(CN)3.