Temperature dependent optical conductivity of undoped cuprates with weak exchange

TL;DR

This study calculates the temperature-dependent optical conductivity of undoped cuprates using a pd-Hubbard model, revealing how exchange interactions influence spectral features and providing insights into magnetic properties of frustrated cuprates.

Contribution

It introduces a detailed finite-temperature analysis of optical conductivity in cuprates, highlighting the impact of exchange interactions on spectral weights and excitations.

Findings

Spectral weights of charge excitations depend strongly on temperature.

Optical conductivity shows dramatic dependence on exchange interaction ratios.

Results enable extraction of exchange interactions from optical spectra.

Abstract

The optical conductivity sigma(omega) is calculated at finite temperature T for CuO_2 chain clusters within a pd-Hubbard model. Data at T = 300 K for Li_2CuO_2 are reanalyzed within this approach. The relative weights of Zhang-Rice singlet and triplet charge excitations near 2.5 and 4 eV, respectively, depend strongly on T, and a rather dramatic dependence of sigma(omega) on the ratio of the first to second neighbor exchange integrals is predicted. On the basis of these results, information about exchange interactionsfor frustrated edge-shared cuprates can be obtained from T-dependent optical spectra. Our results are also relevant for magnetically weakly coupled wide-gap insulators in general.