Material-dependent screening of Coulomb interaction in single-layer cuprates

TL;DR

This study investigates how material differences in cuprate superconductors affect Coulomb interactions and superconducting transition temperatures, using computational methods to explain variations in T_c between Hg1201 and Tl1201.

Contribution

The paper provides a comparative analysis of Coulomb interactions in different cuprates and links these differences to variations in T_c, highlighting the material dependence of superconducting properties.

Findings

Screened on-site Coulomb interaction in Hg1201 is nearly twice that in Tl1201.

Differences in band structure are correlated with oxygen content in buffer layers.

Material-dependent T_c can be explained by variations in Coulomb interactions.

Abstract

To explore material dependence of cuprate superconductors, we evaluate effective Coulomb interactions for Hg1201 and Tl1201, where Tl1201 having a nearly half value of T_c of Hg1201 even at the optimal oxygen concentration. Although structures are similar for these superconductors, there is an apparent difference in the occupied levels below EF. The characteristic difference in the band structure is correlated with oxygen contents in the buffer layer. By using constrained Random Phase Approximation, effective screened Coulomb interactions are estimated for HgBa_2CuO_4 and TlBa_2CuO_5. The results shows that the value of screened on-site Coulomb interaction in Hg1201 is nearly twice bigger than that in Tl1201. In addition, The eigenvalues of the linearized Eliashberg equation of single-band Hubbard model within FLEX can show apparent difference in T_c. When we assume that the twice big screened on-site Coulomb for Hg, the material dependent T_c might be explained.