Folded modes in the infrared spectra of the spin-Peierls phase of CuGeO_3

TL;DR

This study investigates the infrared spectral features of CuGeO_3 across its spin-Peierls transition, identifying folded phonon modes and exploring their relation to spin-phonon interactions.

Contribution

It reports the observation of specific folded phonon modes in CuGeO_3's infrared spectra and discusses their possible connection to spin-phonon coupling effects.

Findings

Detection of spectral lines at 284.2 cm-1 and 311.7 cm-1 appearing at the transition

Identification of these lines as folded modes of the dimerized lattice

Discussion of the role of spin-phonon interaction in spectral features

Abstract

Polarized far-infrared transmittance spectra of CuGeO_3 single crystals were measured at different temperatures (6K < T < 300K). Two spectral lines, at 284.2 cm-1 in E||c polarization and at 311.7 cm-1 in E||b polarization, appear at the temperature of the spin-Peierls transition and grow in intensity with decreasing temperature. Both of them are, most probably, folded modes of the dimerized lattice. We discuss a possible role of the spin-phonon interaction in the formation of the 311.7 cm-1 feature.