Electronic States and Magnetic Propertis of Edge-sharing Cu-O Chains

TL;DR

This study investigates the electronic and magnetic properties of edge-sharing Cu-O chains in copper oxides, revealing differences in optical conductivity, larger charge transfer gaps, and the importance of both nearest and next-nearest neighbor exchange interactions.

Contribution

It provides a systematic analysis of electronic states and magnetic interactions in edge-sharing Cu-O chain compounds, including calculations of exchange interactions and their dependence on bond angles.

Findings

Spectral distribution of optical conductivity differs between edge-sharing and corner-sharing bonds.

Charge transfer gap in edge-sharing chains exceeds that in high-$T_c$ cuprates.

Both $J_1$ and $J_2$ exchange interactions significantly influence magnetic properties.

Abstract

The electronic states and magnetic properties for the copper oxides containing edge-sharing Cu-O chains such as Li$_2$CuO$_2$, La$_6$Ca$_8$Cu$_{24}$O$_{41}$ and CuGeO$_3$ are systematically studied. The optical conductivity $\sigma(\omega)$ and the temperature dependence of the magnetic susceptibility $\chi(T)$ for single crystalline samples Li$_2$CuO$_2$ are measured as a reference system and analyzed by using the exact diagonalization method for small Cu-O clusters. It is shown that the spectral distribution of $\sigma(\omega)$ is different between edge-sharing and corner-sharing Cu-O-Cu bonds. The charge transfer gap in edge-sharing chains is larger than that of high-$T_{c}$ cuprates. The exchange interaction between nearest-neighbor copper ions in edge-sharing chains $J_1$ depends sensitively on the Cu-O-Cu bond angles. In addition to $J_1$, the exchange interaction between next-nearest-neighbor copper ions $J_2$ has sufficient contribution to the magnetic properties. We calculate $J_1$ and $J_2$ for all the copper oxides containing edge-sharing Cu-O chains and discuss the magnetic properties.