Thermodynamic Phase Transitions in Finite Su-Schrieffer-Heeger Chains: Metastability and Heat Capacity Anomalies

TL;DR

This paper explores the thermodynamic phase transitions in finite SSH chains, revealing a metastable phase and heat capacity anomalies linked to finite-size effects and topology, with implications for experimental systems.

Contribution

It uncovers a metastable thermodynamic phase and heat capacity anomalies in finite SSH chains, highlighting the interplay between topology, finite size, and thermal fluctuations.

Findings

Identification of a metastable phase with a local heat capacity minimum.

Observation of a second-order phase transition distinct from topological transition.

Enhanced metastability with increased hopping asymmetry and chain length.

Abstract

We investigate the thermodynamic properties of finite Su-Schrieffer-Heeger (SSH) chains in thermal equilibrium at fixed temperature and chemical potential. Using the canonical and grand canonical ensembles, we calculate the energy density, particle number density, entropy, and heat capacity as functions of temperature, chemical potential, and hopping asymmetry. Our analysis reveals the emergence of a metastable thermodynamic phase characterized by a local minimum in the heat capacity for non-dimerized configurations, signaling a second-order phase transition distinct from the topological phase transition. This metastable phase becomes more pronounced as the hopping asymmetry increases and the chain length grows. We demonstrate that while the topological properties are determined by boundary states, the bulk thermodynamic behavior exhibits rich phase structure that can be tuned through the hopping parameter ratio. These findings provide insights into the interplay between topology, finite-size effects, and thermal fluctuations in one-dimensional topological systems, with potential implications for experimental realizations in cold atoms, photonic systems, and topoelectrical circuits.