A New Approach to Quantum Spin Chains at Finite Temperature

Abstract

Presented is a new approach to the study of one dimensional quantum spin systems at finite temperature. The approach is based upon a general structure of solvable models; the Yang-Baxter equation and the Bethe ansatz equation, and in addition the evaluation of finite size corrections. Provided that the ground state is constructed by the Bethe ansatz method, exact low temperature expansions of physical quantities are given without further assumption.