Low Temperature Physics

Low-temperature properties of finite XX-chains with additional Ising spin

A. V. Artemov, E. V. Ezerskaya

Published Dec 1, 2018• 0 citations

Abstract

This is a theoretical study of quantum stationary states and thermodynamics of two exactly solvable quantum models: a finite XX-chain with an “offshoot” that is connected via ZZ-interaction (Ising) to one of the chain nodes, and two different finite XX-chains joined through an additional ZZ-spin. It is shown that the spectrum can have impurity levels localized near the impurity spin, and the conditions for their manifestation are determined. The field and temperature dependences of the main thermodynamic characteristics of the models are investigated.

DOI: 10.1063/1.5078616

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Low Temperature Physics

Low-temperature properties of finite XX-chains with additional Ising spin

A. V. Artemov, E. V. Ezerskaya

Published Dec 1, 2018• 0 citations

Publisher

Abstract

DOI: 10.1063/1.5078616

Related papers

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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.