Spin-orbital physics in the optical conductivity of quarter-filled manganites

TL;DR

This study uses finite-temperature diagonalization to analyze the optical conductivity and spin-orbital dynamics in half-doped manganites, revealing a broad spectrum with an optical gap and temperature-dependent shifts.

Contribution

It provides new insights into the temperature evolution of optical conductivity and spin-orbital interactions in the CE phase of manganites.

Findings

Optical conductivity shows a broad spectrum with a charge-order-induced gap.

Temperature increase causes a shift of spectral weight to lower energies.

In-gap absorption due to orbiton-spin excitations observed at low temperatures.

Abstract

Using finite-temperature diagonalization we investigate the optical conductivity $\sigma(\omega)$ and spin-orbital dynamics in the CE phase of half-doped manganites. We find $\sigma(\omega)$ characterized by a broad spectrum with pronounced optical gap due to charge ordering induced by Coulomb and further neighbor Jahn-Teller interactions. With increasing temperature the conductivity shows a significant change over a wide energy range with a characteristic shift towards lower frequencies. In the low temperature CE phase we observe in-gap absorption due to combined orbiton-spin excitations.