Spin dynamics of the spin-Peierls compound CuGeO_3 under magnetic field

TL;DR

This paper investigates the effects of magnetic fields on the spin dynamics of CuGeO_3, revealing how the spin gap closes and incommensurate excitations emerge, with implications for experimental detection methods.

Contribution

It provides a numerical analysis of the field-dependent spin dynamical structure factor and static susceptibility in CuGeO_3, highlighting the transition behavior and experimental signatures.

Findings

Strong field dependence of transverse susceptibility in dimerized phase

Emergence of incommensurate low energy spin excitations above critical field

Potential experimental detection through NMR and spin-echo relaxation rates

Abstract

The magnetic field--driven transition in the spin-Peierls system CuGeO_3 associated with the closing of the spin gap is investigated numerically. The field dependence of the spin dynamical structure factor (seen by inelastic neutron scattering) and of the momentum dependent static susceptibility are calculated. In the dimerized phase (H<H_c), we suggest that the strong field dependence of the transverse susceptibility could be experimentally seen from the low temperature spin-echo relaxation rate 1/T_{2G} or the second moment of the NMR spectrum. Above H_c low energy spin excitations appear at incommensurate wave vectors where the longitudinal susceptibility chi_{zz}(q) peaks.