Mean-field theory of the spin-Peierls systems: Application to CuGeO3

TL;DR

This paper develops a mean-field theoretical framework for spin-Peierls systems, specifically applied to CuGeO3, improving predictions of ground state and gap energies, and analyzing the competition between magnetic orders.

Contribution

It introduces an enhanced mean-field model based on an alternating bond order parameter for two-dimensional dimerized Heisenberg systems, advancing understanding of CuGeO3.

Findings

Improved ground state and gap energy predictions in 1D limit.

Analysis of antiferromagnetic and spin-Peierls order competition in 2D.

Lowest energy gap lacks singlet-triplet character, aligning with experimental data.

Abstract

A mean-field theory of the spin Peierls systems based on the two dimensional dimerized Heisenberg model is proposed by introducing an alternating bond order parameter. Improvements with respect to previous mean-field results are found in the one-dimensional limit for the ground state and the gap energies. In two dimensions, the analysis of the competition between antiferromagnetic long range order and the spin-Peierls ordering is given as a function of the coupling constants. We show that the lowest energy gap to be observed does not have a singlet-triplet character in agreement with the low temperature thermodynamic properties of CuGeO3.