Role of Charge Density Wave in Superconductivity of Organic Conductor α-(BEDT-TTF)_2NH_4Hg(SCN)_4 Salt(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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The superconductivity in quasi-two-dimensional organic conductor α-(BEDT-TTF)_2NH_4Hg(SCN)_4, which occurs in the vicinity of charge density wave phase, has been investigated using the extended Hubbard model with both on-site repulsive interaction and nearest-neighbor repulsive interactions, and with the hopping energy estimated from the X-ray experiment. The pairing interactions induced by the spin and charge fluctuations are calculated in terms of the random phase approximation. The repulsive interactions are chosen so that the characteristic momentum of the charge fluctuation reproduces that of the X-ray diffuse scattering experiment. From the linearized gap equation, it is shown that the pairing for the singlet superconductivity is determined by the charge fluctuation. A good correspondence with the experiment is obtained for the pressure dependence of the superconducting transition temperature T_c, which exhibits a maximum under uniaxial pressure.
社団法人日本物理学会の論文
2007-01-15