Ground State Structure and Low Temperature Behaviour of an Integrable Chain with Alternating Spins

TL;DR

This paper investigates the ground state and low-temperature properties of an integrable alternating-spin chain, analyzing thermodynamic behavior and susceptibilities, especially near phase transitions, using the thermodynamic Bethe ansatz.

Contribution

It extends previous work by analyzing the thermodynamic Bethe ansatz for the model with differing coupling signs and calculates low-temperature thermodynamic quantities.

Findings

Calculated heat capacity and magnetic susceptibility at low temperature for the conformally invariant case.

Analyzed susceptibilities near phase transition lines at zero temperature.

Provided insights into the ground state structure of the alternating-spin chain.

Abstract

In this paper we continue the investigation of an anisotropic integrable spin chain, consisting of spins $s=1$ and $s=\frac{1}{2}$, started in our paper \cite{meissner}. The thermodynamic Bethe ansatz is analysed especially for the case, when the signs of the two couplings $\bar{c}$ and $\tilde{c}$ differ. For the conformally invariant model ($\bar{c}=\tilde{c}$) we have calculated heat capacity and magnetic susceptibility at low temperature. In the isotropic limit our analysis is carried out further and susceptibilities are calculated near phase transition lines (at $T=0$).