Electronic Heat Capacity
of a Single-Component Molecular Conductor

We have performed a thermodynamic investigation of a single component molecular conductor [Au(tmdt)2] in order to confirm the realization of a metal ground state. This material is designed and synthesized by the strategy to decrease HOMO-LUMO gap and increase the overlaps of neighboring molecules in the crystalline structure by Profs. A. Kobayashi and H. Kobayashi. The heat capacity measurements were performed by the relaxation calorimetry technique using compressed pellet samples at low temperatures. Although some traces of paramagnetic impurities were observed by studying the magnetic fields dependence, the existence of a T-linear term which is not affected by the external fields was confirmed. The electronic heat capacity coefficient γ is estimated to be about 10 mJ K−2 mol−1, which is consistent with the result of the paramagnetic susceptibility measurement. The observation supports the realization of metallic ground state in this compound.

(by Y. Inoue & Y. Nakazawa)

	Fig. 1. Molecular structure of [M(tmdt)2], where tmdt is trimethylenetetrathiafulvalenedithiolate.
	Fig. 2. Temperature dependence of the heat capacity of [Au(tmdt)2] obtained by a compressed pellet sample. The broad hump observed around 4 K is considered as an extra contribution of phonons owing to the the libration of stacked molecules.
	Fig. 3. Low-temperature heat capacity of [Au(tmdt)2] shown as a Cp T−1 vs T2 plot. The existence of electronic heat capacity coefficient of about 10 mJ K−2 mol−1 is observable.