Multiorbital analysis of the effects of uniaxial and hydrostatic pressure on $T_c$ in the single-layered cuprate superconductors

TL;DR

This study uses a two-orbital model to theoretically analyze how uniaxial and hydrostatic pressures affect the critical temperature in single-layer cuprate superconductors, revealing that less hybridization of certain orbitals correlates with higher $T_c$.

Contribution

It introduces a first-principles derived two-orbital model analyzed with fluctuation exchange approximation to explain pressure effects on $T_c$ in cuprates.

Findings

Pressure increases $T_c$ under hydrostatic conditions.

Uniaxial pressure effects depend on the axis, increasing or decreasing $T_c$.

Higher $T_c$ is linked to reduced hybridization of specific orbitals.

Abstract

The origin of uniaxial and hydrostatic pressure effects on $T_c$ in the single-layered cuprate superconductors is theoretically explored. A two-orbital model, derived from first principles and analyzed with the fluctuation exchange approximation gives axial-dependent pressure coefficients, $\partial T_c/\partial P_a>0$, $\partial T_c/\partial P_c<0$, with a hydrostatic response $\partial T_c/\partial P>0$ for both La214 and Hg1201 cuprates, in qualitative agreement with experiments. Physically, this is shown to come from a unified picture in which higher $T_c$ is achieved with an "orbital distillation", namely, the less the $d_{x^2-y^2}$ main band is hybridized with the $d_{z^2}$ and $4s$ orbitals higher the $T_c$. Some implications for obtaining higher $T_c$ materials are discussed.