Material Optimization for Fermi Surface Shape Control of Tl-based Cuprate Superconductors

TL;DR

This study proposes an element substitution optimization method for cuprate superconductors, analyzing Fermi surface shapes via DFT-GGA to predict structures that could enhance superconducting transition temperatures.

Contribution

It introduces a systematic approach to optimize cuprate superconductor properties by controlling Fermi surface shape through element substitution based on DFT calculations.

Findings

Smaller Fermi surface shape parameter r correlates with potential Tc enhancement.

Element substitution affects the Fermi surface and superconducting properties systematically.

The method can predict optimized cuprate structures based on known superconductors.

Abstract

To show an optimization method of element substitution for cuprate superconductors, we investigate Fermi surface shape of TlR2A2Cu3O9 with R=La, Y, and A=Li, Na, K, Rb, Cs. We adopt the generalized gradient approximation in the density-functional theory (DFT-GGA) for the study of over-doped phases of these unknown cuprates. The electronic structures of crystals optimized by DFT-GGA show systematic element dependence in a Fermi surface shape controlling parameter, r, of Cu dx2-y2 bands, where nearly absent dz2 component at the Fermi level and smaller r keeping t1 suggest enhancement of the superconducting transition temperature within the spin-fluctuation mechanism. For TlYRb2Cu3O9, smaller r by a reduction factor larger than 10% compared to a reference system of TlBa2Ca2Cu3O9 (TBCCO) appears in the outer CuO2 plane, but with 12 % reduction in t1. For TlR2Li2Cu3O9, (R=Y, La), smaller r by a factor larger than 1% appears keeping t1 as large as TBCCO in the inner plane. Our method may be used to predict an optimized material structure referencing known cuprate superconductors.