Enhancement of electron correlation due to the molecular dimerization in organic superconductors beta-(BDA-TTP)(2)X (X = I-3, SbF6)

Article

关键词: BDA-TTP;    CONDUCTORS;   

DOI  :  10.1103/PhysRevB.92.155108

来源: SCIE

【 摘 要 】

We perform a first-principles band calculation for quasi-two-dimensional organic superconductors beta-(BDATTP)(2)I-3 and beta-(BDA-TTP)(2)SbF6. The first-principles band structures between the I-3 and SbF6 salts are apparently different. We construct a tight-binding model for each material which accurately reproduces the first-principles band structure. The obtained transfer energies give the differences as follows: (i) larger dimerization in the I-3 salt than the SbF6 salt, and (ii) different signs and directions of the interstacking transfer energies. To decompose the origin of the difference into the dimerization and the interstacking transfer energies, we adopt a simplified model by eliminating the dimerization effect and focus only on the difference caused by the interstacking transfer energies. From the analysis using the simplified model, we find that the difference of the band structure comes mainly from the strength of the dimerization. To compare the strength of the electron correlation having roots in the band structure, we calculate the physical properties originating from the effect of the electron correlation such as the spin susceptibility applying the two-particle self-consistent method. We find that the maximum value of the spin susceptibility for the I-3 salt is larger than that of the SbF6 salt. Hypothetically decreasing the dimerization within the model of the I-3 salt, the spin susceptibility takes almost the same value as that of the SbF6 salt for the same magnitude of the dimerization. We expect that the different ground state between the I-3 and SbF6 salt mainly comes from the strength of the dimerization which is apparently masked in the band calculation along a particular k path.

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