Thermal study of reentrant metal-insulator transition in deuterated (DMe-DCQNI)(2)Cu

We have investigated thermal properties (specific heat and latent heat) of selectively deuterated (DMe-DCNQI)(2)Cu in the temperature region (0.5K<T<100K) with the particular interest in the mechanism of mysterious reentrant metal-insulator transition. Specific heat steeply reduces as crossing from higher temperature metallic states (HM) to insulator states (I). We have succeeded in precisely determining the latent heat at the HM-I transition. In metallic phase, the electron entropy has the linear temperature dependence like gamma T term. We clarified that the competition between these gamma T contributions in metallic phase and freedom of Cu2+ spins in insulator phase drives the reentrant M-I transition.