%0 Journal Article
%T Thermodynamic Properties of 百-(BEDT-TTF)2X Salts: Electron Correlations and Superconductivity
%A Yasuhiro Nakazawa
%A Satoshi Yamashita
%J Crystals
%D 2012
%I MDPI AG
%R 10.3390/cryst2030741
%X Heat capacity measurements of 百-(BEDT-TTF) 2 X (BEDT-TTF: Bis(ethylendithio) tetrathiafulvalene, X: counteranions) which are classified as two-dimensional (2D) dimer-Mott system are reported. At first, we explain structural and electronic features originated from rigid dimerization in donor arrangement in 2D layers. The antiferromagnetic Mott insulating phase located at low-pressure region in the phase diagram shows vanishing 污 electronic heat capacity coefficient in the heat capacity, which claims opening of a charge-gap in this insulating state. Then, a systematic change of the 污 around the Mott boundary region is reported in relation to the glass freezing of ethylene dynamics. The thermodynamic parameters determined by ˋ Cp/ 污T c of 10 K class superconductors, 百-(BEDT-TTF) 2Cu(NCS) 2 and 百-(BEDT-TTF) 2Cu[N(CN) 2]Br demonstrate that a rather large gap with a strong coupling character appears around the Fermi-surface. On the other hand, the low temperature heat capacity clearly shows a picture of nodal-gap structure due to an anisotropic pairing. The comparison with lower T c compounds in the 百-type structure is also performed so as to discuss overall features of the 百-type superconductors. The heat capacity measurements of hole-doped systems containing mercury in the counteranions show an anomalous enhancement of 污, which is consistent with the T 1 ˋ1 of NMR experiments etc. The results of heat capacity measurements under high pressures are also reported.
%K heat capacity
%K electron correlation
%K Mott insulator
%K organic superconductors
%U http://www.mdpi.com/2073-4352/2/3/741