Dielectric Response of Multiorbital Molecular Compounds (TTM-TTP)X (X = AuI₂and I₃)

The temperature dependence of the dielectric constant in the organic molecular compounds (TTM-TTP)X (X = AuI₂, I₃) was investigated, where the intramolecular charge degrees of freedom arising from the mixing of orbitals are discussed.We observed a large relaxor-like dielectric anomaly in single crystals along the TTM-TTP molecular long axis but not along the short axis as well as the suppression of such anomaly under dc bias fields. These results indicate the intramolecular charge fluctuation between two fragments of the molecular orbitals in one TTM-TTP molecule with inhomogeneity. The relations between the anomaly, natural defects, spin singlet transition, and unpaired localized spins are discussed.