The microscopic spin-phonon coupling constants in CuGeO_3

TL;DR

This paper determines the microscopic spin-phonon coupling constants in CuGeO_3 using theoretical models and experimental data, providing insights into the material's spin-lattice interactions and thermal properties.

Contribution

It provides the first detailed calculation of spin-phonon coupling constants in CuGeO_3, linking microscopic theory with experimental observations.

Findings

Coupling constants are consistent with microscopic theories.

The c-axis thermal expansion anomaly is explained.

Values of coupling constants are provided for an effective Hamiltonian.

Abstract

Using RPA results, mean field theory, and refined data for the polarization vectors we determine the coupling constants of the four Peierls-active phonon modes to the spin chains of CuGeO_3. We then derive the values of the coupling of the spin system to the linear ionic displacements, the bond lengths and the angles between bonds. Our values are consistent with microscopic theories and various experimental results. We discuss the applicability of static approaches to the spin-phonon coupling. The c-axis anomaly of the thermal expansion is explained. We give the values of the coupling constants in an effective one-dimensional Hamiltonian.