Spin-Peierls Transition in CuGeO_3: Critical, Tricritical, or Mean Field?

TL;DR

This paper investigates the nature of the spin-Peierls transition in CuGeO_3, demonstrating that its critical behavior can be modeled with a mean field approach that includes a tricritical to mean field crossover.

Contribution

The study provides a quantitative mean field model that captures the crossover from tricritical to mean field behavior near the phase transition in CuGeO_3.

Findings

Order parameter behavior fits mean field model

Magnetic energy gap and heat capacity are well described

Transition region shows tricritical to mean field crossover

Abstract

The spin-Peierls phase transition in CuGeO_3 has been extensively studied utilizing a variety of experimental techniques. Interpretations of the phase transition behavior vary from tricritical to mean field to Ising critical to XY critical. We show that the behavior in the vicinity of the phase transition of each of the order parameter, the magnetic energy gap and the heat capacity can be quantitatively fitted with few adjustable parameters with a mean field model incorporating a tricritical to mean field critical crossover in the transition region.