Effects of excess or deficiency of oxygen content on the electronic structure of high-$T_C$ cuprates

TL;DR

This study uses band structure calculations to explore how excess or deficient oxygen affects the electronic properties of high-$T_C$ cuprates, revealing complex doping effects and their influence on magnetic fluctuations.

Contribution

It provides detailed computational analysis of oxygen vacancies and interstitials in cuprates, highlighting their impact on electronic structure and magnetic behavior.

Findings

Oxygen vacancies in BCO act as electron dopants.

Oxygen interstitials increase the density of states at the Fermi level.

Oxygen defects influence antiferromagnetic spin fluctuations.

Abstract

Band structure calculations are presented for large supercells of Ba$_2$CuO$_4$ (BCO) with O-vacancies in planar or apic al positions, and of superoxygenated La$_2$CuO$_4$ (LCO) with oxygen interstitials in the La$_2$O$_2$ layers. It is foun d that apical oxygen vacancies in BCO act as electron dopants and makes the electronic structure similar to that of hole doped LCO. Excess oxygen interstitials forming wires in the La$_2$O$_2$ layers of LCO are shown to yield a much larger density-of-states at the Fermi energy than for the stoichiometric compound related with a segmentation of the Fermi surface. Anti-ferromagnetic (AFM) spin fluctuations are strengthened by O-vacancies in BCO as well as by oxygen interstitials in LCO, but are strongly suppressed in O-deficient LCO. Our results indicate the complexity of doping by O-vacancies, and by ordered defects that are a significant factor contr olling the electronic properties of cuprates.