Thermodynamics of a Spin-1/2 Chain Coupled to Einstein Phonons

TL;DR

This paper uses high order series expansion to analyze the thermodynamics of a spin-1/2 chain coupled to Einstein phonons across different regimes, revealing the impact of phonons on thermodynamic properties.

Contribution

It introduces a method that avoids truncating phonon space, enabling detailed analysis of phonon effects in various parameter regimes.

Findings

Dynamic phonon effects influence multiple thermodynamic quantities.

The method effectively explores adiabatic, antiadiabatic, and intermediate regimes.

Results provide insights into phonon contributions without approximating phonon states.

Abstract

A high order series expansion is employed to study the thermodynamical properties of a S=1/2 chain coupled to dispersionless phonons. The results are obtained without truncating the phonon subspace since the series expansion is performed formally in the overall exchange coupling J. The results are used to investigate various parameter regimes, e.g. the adiabatic and antiadiabatic limit as well as the intermediate regime which is difficult to investigate by other methods. We find that dynamic phonon effects become manifest when more than one thermodynamic quantity is analyzed.