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

To explore the material dependence of cuprate superconductors, we evaluate effective Coulomb interactions for Hg1201 and Tl1201, where Tl1201 has nearly half value of T-c 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 E-F. 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 T-c. When we assume that the screened on-site Coulomb interaction is twice as large for Hg as for Tl, the material-dependent T-c can be explained.