Fig. 1. Temperature dependences of low-temperature heat capacity plotted as CpT −1 vs T −2. The finite electronic heat capacity coefficient scales to the static magnetic susceptibility value at T = 0 K.
In the case of triangular lattice with two-dimensional structure, the geometric frustration prohibits the formation of ordering and a liquid-like ground state of spins is suggested. In this work, we discuss common nature of thermodynamic behaviors of two organic charge transfer salts, κ-(BEDT-TTF)2Cu2(CN)3 and EtMe3Sb[Pd(dmit)2]2 which show spin liquid behaviors at low temperatures. From the heat capacity data in the low temperature region, we have confirmed that the low energy excitations have a gap-less character. The determined electronic heat capacity coefficients γ's of both salts scale to the magnetic susceptibility values extrapolated down to T = 0. The Wilson ration is evaluated as 1.10 for κ-(BEDT-TTF)2Cu2(CN)3 and 1.13 for EtMe3Sb[Pd(dmit)2]2, which is close to the non correlated Fermi-liquid state in metallic system. Furthermore, we discuss on the anomalous lattice heat capacity of these triangular lattice compounds appear in the heat capacity in both compounds. In spite of these common features, the phase diagram and pressure effects in two compounds are different due to the difference of stacking pattern of dimer units in the two-dimensional layers.
|
|
Fig. 1. Temperature dependences of low-temperature heat capacity plotted as CpT −1 vs T −2. The finite electronic heat capacity coefficient scales to the static magnetic susceptibility value at T = 0 K. |