Ginzburg-Landau theory of phase transitions in quasi-one-dimensional systems

TL;DR

This paper develops a Ginzburg-Landau theoretical framework for phase transitions in quasi-one-dimensional materials, emphasizing the importance of intrachain fluctuations and providing quantitative predictions for transition properties.

Contribution

It introduces a Ginzburg-Landau model that accurately incorporates intrachain fluctuations, offering new insights into three-dimensional phase transitions in weakly coupled chain systems.

Findings

Intrachain fluctuations are crucial and must be treated exactly.

The width of the critical region is about 5-8% of the transition temperature.

Computed transition temperature, specific heat jump, and coherence lengths.

Abstract

A wide range of quasi-one-dimensional materials, consisting of weakly coupled chains, undergo three-dimensional phase transitions that can be described by a complex order parameter. A Ginzburg-Landau theory is derived for such a transition. It is shown that intrachain fluctuations in the order parameter play a crucial role and must be treated exactly. The effect of these fluctuations is determined by a single dimensionless parameter. The three-dimensional transition temperature, the associated specific heat jump, coherence lengths, and width of the critical region, are computed assuming that the single chain Ginzburg-Landau coefficients are independent of temperature. The width of the critical region, estimated from the Ginzburg criterion, is virtually parameter independent, being about 5-8 per cent of the transition temperature. To appear in {\it Physical Review B,} March 1, 1995.