Correlated electronic structure of high-temperature superconductor Ba$_2$CuO$_{3+\delta}$

TL;DR

This study uses advanced computational methods to explore the electronic structure of a high-temperature superconductor with unique CuO plane arrangements, revealing new correlated physics and potential superconducting regions.

Contribution

It introduces a detailed DFT+DMFT analysis of Ba$_2$CuO$_{3+\delta}$ with mixed CuO plane structures, highlighting novel correlated electronic behaviors.

Findings

Cu atoms maintain a 3d$^9$ configuration despite structural differences.

Quasi-1D CuO planes are slightly hole-doped Mott insulators.

O-depleted CuO$_2$ planes are more hole-doped and may host superconductivity.

Abstract

Cuprate superconductors have attracted extensive attention due to high critical temperatures. Conventional cuprates typically contain perfect CuO$_2$ planes which are considered as a key factor to superconductivity since the superconductivity takes place in them. However, in Ba$_2$CuO$_{3+\delta}$ with $\delta=0.2$ and O-depleted CuO$_2$ planes, superconductivity still arises even with a transition temperature as high as 73 K. Using combined density functional theory and dynamical mean-field theory (DFT+DMFT) calculations, we investigated the electronic correlation and electronic structure of Ba$_2$CuO$_{3.25}$ with alternating quasi-one-dimensional (1D) CuO planes and O-depleted CuO$_2$ planes. We find that although different from the usual cuprates, the Cu atoms are still dominated by a 3$d^9$ configuration and the system is of a new kind of correlated single-orbital physics. The quasi-1D CuO planes, composed of parallel Cu-O chains, are slightly hole-doped quasi-1D Mott insulator, while the O-depleted CuO$_2$ planes are more hole doped, with a 2D correlated electronic structure, and may host superconductivity.