Photoinduced Growth of Ferroelectric Charge Order in Organic Dimer-Mott insulator

Layered triangular organic dimer Mott (DM) insulator kappa-(ET)(2)Cu-2(CN)(3) was shown to exhibit a relaxor-like dielectric anomaly below 40 K with strong dispersion relation, reflecting its electric dipole glass (ferroelectric charge order; FCO) nature[1, 2]. The dielectric anomaly in kappa-(ET)(2)Cu-2(CN)(3) indicates that this compound is located in the vicinity of the DM-FCO phase boundary, where ferroelectric fluctuation such as the electric dipole glass state or the polar cluster is formed in the DM phase. Optical excitation of the DM-FCO competing state by an ultrashort light pulse enables us to achieve dramatic responses, such as photoinduced ferroelectricity, photoinduced growth of the electric dipole glass or the polar clusters.