Temperature Correlation of Quantum Spins

TL;DR

This paper reviews historical calculations of temperature-dependent correlation functions in quantum spin chains and related models, highlighting exponential decay behavior and explicit decay rates.

Contribution

It summarizes key results on correlation functions in quantum many-body models, emphasizing the explicit evaluation of decay rates in 1993 and subsequent similar findings.

Findings

Correlation functions decay exponentially with space and time.

Decay rates can be explicitly calculated.

Similar exponential decay results apply to various models.

Abstract

This is a historical note. In 1993 we calculated space, time and temperature dependent correlation function in isotropic version of one dimensional XY spin chain. The correlation function decays exponentially with time and space separation. The rate of exponential decay was evaluated explicitly. Since that time similar results were obtained in other models: Bose gas with delta interaction, Ising model and strongly correlated electrons.