Material-Dependent Screening of Coulomb Interaction in Single-Layer Cuprates

Abstract

To explore the material dependence of cuprate superconductors, we evaluate effective Coulomb interactions for Hg1201 and Tl1201, where Tl1201 has nearly half value of Tc as that of Hg1201 even at the optimal oxygen concentration. Although the structures of these superconductors are similar, there is an apparent difference in the occupied levels below EF. The characteristic difference in the band structure is correlated with the oxygen content in the buffer layer. By using a constrained random phase approximation, effective screened Coulomb interactions are estimated for HgBa2CuO4 and TlBa2CuO5. The results show that the screened on-site Coulomb interaction in Hg1201 is nearly twice as large as that in Tl1201. In addition, the eigenvalues of the linearized Eliashberg equation of the single-band Hubbard model within the fluctuation exchange approximation can explain the apparent difference in Tc. When we assume that the screened on-site Coulomb interaction is twice as large for Hg as for Tl, the material-dependent Tc can be explained.