Optical absorption spectra in SrCu_2O_3 two-leg spin ladder

TL;DR

This paper calculates and compares phonon-assisted optical absorption spectra in SrCu_2O_3 two-leg spin ladders using two models, highlighting spectral features that distinguish the models and aid in identifying the correct physical description.

Contribution

It introduces a detailed comparison of optical spectra predictions from models with and without cyclic four-spin interactions for SrCu_2O_3.

Findings

Shoulder at 978 cm^{-1} in cyclic four-spin model

Peak at 1975 cm^{-1} in cyclic four-spin model

Peak at 1344 cm^{-1} in pure two-leg ladder model

Abstract

We calculate the phonon-assisted optical-absorption spectra in SrCu_2O_3 two-leg spin-ladder systems. The results for two models proposed for SrCu_2O_3 are compared. In the model including the effects of a cyclic four-spin interaction, the shoulder structure appears at 978 cm^{-1} and the peak appears at 1975 cm^{-1} in the spectrum for polarization of the electric field parallel to the legs. In the other model which describes a pure two-leg ladder, the peak appears around the lower edge of the spectrum at 1344 cm^{-1}. The feature can be effective in determining the proper model for SrCu_2O_3.