Spin Liquid State in Charge Transfer Complex EtMe3Sb [Pd(dmit)2]2

A series of organic charge transfer salts of X[Pd(dmit)2]2 show various kinds of ground states by changing cation (X+).We have measured low-temperature heat capacities of EtMe3Z[Pd(dmit)2]2 (Z = Sb, As, P). The temperature dependence of heat capacity of EtMe3Sb[Pd(dmit)2]2 shows linear relation with finite values, despite that the other samples do not show the linear relation with finite values. From this fact, we can confirm the realization of quantum spin liquid in EtMe3Sb[Pd(dmit)2]2 sample. We have also found a considerable difference in heat capacities by the difference of cations. The values of CpT-1 of EtMe3Sb[Pd(dmit)2]2 is twice as large as those of EtMe3P[Pd(dmit)2]2 at 7 K. The difference of heat capacity is attributable to the difference of lattice contribution in heat capacity.

(S. Yamashita & T. Yamamoto)

	Fig.1 The schematic figures of (a) quantum spin liquid state and (b) valence bond solid (vbs) state.
	Fig.2 The temperature dependence of heat capacity of EtMe3Z[Pd(dmit)2]2 (Z=Sb, As, P). The EtMe3Sb[Pd(dmit)2]2 shows linear relation with finite values.
	Fig.3 CpT-1 vs T2 plot of EtMe3P[Pd(dmit)2]2 and EtMe3Sb[Pd(dmit)2]2 obtained in a temperature range between 0.8 K and 7 K. There is considerable difference in heat capacities by the difference of cations.