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

We have investigated thermal properties (specific heat and latent heat) of selectively deuterated (DMe-DCNQI)2Cu 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 γT term. We clarified that the competition between these γT contributions in metallic phase and freedom of Cu2+ spins in insulator phase drives the reentrant M-I transition.