Soliton Lattices in the Incommensurate Spin-Peierls Phase: Local Distortions and Magnetizations

TL;DR

This paper investigates how zero-point fluctuations of soliton lattices in CuGeO_3 influence NMR line widths, reconciling experimental and theoretical discrepancies through the role of phasonic excitations and frustration effects.

Contribution

It demonstrates the impact of nonadiabatic soliton lattice fluctuations on NMR line widths and explains the difference between X-ray and NMR measurements in the spin-Peierls phase.

Findings

Zero-point motion reduces NMR line widths.

Discrepancy between X-ray and NMR widths explained by magnetic vs. distortive effects.

Frustration controls the ratio of these widths.

Abstract

It is shown that nonadiabatic fluctuations of the soliton lattice in the spin-Peierls system CuGeO_3 lead to an important reduction of the NMR line widths. These fluctuations are the zero-point motion of the massless phasonic excitations. Furthermore, we show that the discrepancy of X-ray and NMR soliton widths can be understood as the difference between a distortive and a magnetic width. Their ratio is controlled by the frustration of the spin system. By this work, theoretical and experimental results can be reconciled in two important points.