Thermodynamics of the Heisenberg XXX chain with negative spin

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Hauptverfasser: Zhong, Rong, Chen, Yang-Yang, Hao, Kun, Yang, Wen-li, Korepin, Vladimir
Format: Preprint
Veröffentlicht: 2026
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author Zhong, Rong
Chen, Yang-Yang
Hao, Kun
Yang, Wen-li
Korepin, Vladimir
author_facet Zhong, Rong
Chen, Yang-Yang
Hao, Kun
Yang, Wen-li
Korepin, Vladimir
contents We study the thermodynamics of the isotropic Heisenberg XXX spin chain with negative spin, focusing on the case $s=-1$. The model is equivalent to the quantum lattice nonlinear Schrödinger (NLS) model and appears as an effective theory in deep inelastic scattering in high-energy quantum chromodynamics. Owing to its integrability, it admits a consistent Bethe Ansatz description and a well-defined thermodynamic limit. Using the thermodynamic Bethe Ansatz, we analyze the ground state, elementary excitations, and finite-temperature properties. In contrast to the conventional positive spin XXX chain, the negative spin model exhibits a distinct vacuum structure and excitation spectrum, leading to modified TBA equations and unconventional low-temperature behavior. Although the integral equations resemble those of the Lieb-Liniger Bose gas, the thermodynamics and scaling properties are qualitatively different and cannot be continuously connected. We derive the free energy, entropy, and specific heat, and identify a quantum phase transition separating different thermodynamic regimes. At zero temperature, the excitation spectrum becomes linear in the continuum limit and can be described by a conformal field theory. The low-temperature regime realizes a Luttinger-liquid like phase with features unique to the negative spin XXX chain.
format Preprint
id arxiv_https___arxiv_org_abs_2602_03714
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Thermodynamics of the Heisenberg XXX chain with negative spin
Zhong, Rong
Chen, Yang-Yang
Hao, Kun
Yang, Wen-li
Korepin, Vladimir
High Energy Physics - Theory
Statistical Mechanics
Quantum Physics
We study the thermodynamics of the isotropic Heisenberg XXX spin chain with negative spin, focusing on the case $s=-1$. The model is equivalent to the quantum lattice nonlinear Schrödinger (NLS) model and appears as an effective theory in deep inelastic scattering in high-energy quantum chromodynamics. Owing to its integrability, it admits a consistent Bethe Ansatz description and a well-defined thermodynamic limit. Using the thermodynamic Bethe Ansatz, we analyze the ground state, elementary excitations, and finite-temperature properties. In contrast to the conventional positive spin XXX chain, the negative spin model exhibits a distinct vacuum structure and excitation spectrum, leading to modified TBA equations and unconventional low-temperature behavior. Although the integral equations resemble those of the Lieb-Liniger Bose gas, the thermodynamics and scaling properties are qualitatively different and cannot be continuously connected. We derive the free energy, entropy, and specific heat, and identify a quantum phase transition separating different thermodynamic regimes. At zero temperature, the excitation spectrum becomes linear in the continuum limit and can be described by a conformal field theory. The low-temperature regime realizes a Luttinger-liquid like phase with features unique to the negative spin XXX chain.
title Thermodynamics of the Heisenberg XXX chain with negative spin
topic High Energy Physics - Theory
Statistical Mechanics
Quantum Physics
url https://arxiv.org/abs/2602.03714