Study of spin-Peierls transition in alpha'--NaV2O5 by infrared reflectivity

TL;DR

This study investigates the spin-Peierls transition in alpha'-NaV2O5 using polarized infrared reflectivity, revealing spectral features linked to dimerization and providing theoretical insights into the transition's nature.

Contribution

It presents detailed infrared measurements of alpha'-NaV2O5 across the transition and offers theoretical models to interpret the spectral features and dimerization process.

Findings

Spectral features associated with dimerization detected in both polarizations.

The 718 cm^-1 spectral line sharply rises below T_SP, following a specific power law.

A continuum signal persists across all temperatures in the a-polarized spectra.

Abstract

Polarized infrared reflectivity measurements have been performed on single crystals of the spin-Peierls compound alpha'-NaV2O5 in the temperature range 20-300 K. Pronounced spectral features associated with the formation of the dimerized phase were detected both in the a- and b-polarizations (perpendicular and parallel to the spin-1/2 chains, respectively). The temperature dependence of a salient spectral line at 718 cm^-1 sharply rising below the transition temperature T_SP obeys a (1-T/T_SP)^(2beta) law with T_SP \simeq 34.3$K and beta \simeq 0.25. In addition, a continuum signal is observed in the whole temperature range in the a-polarized optical conductivity spectra. In order to interpret these results, calculations of the static dimerization and of the optical conductivity based on a mean-field and a dynamical treatment of the lattice respectively are proposed.