Integrable spin-1 Heisenberg chain with impurity

Abstract

We construct an integrable SU(2)-invariant model consisting of the Heisenberg chain of spin 1 interacting with an impurity of spin S. This generalizes previous results by Andrei and Johannesson for the spin-(1/2 chain. The model Hamiltonian is diagonalized and the thermodynamics is obtained. For ferromagnetic coupling at low temperatures the impurity susceptibility diverges as $T^{\mathrm{-}2}$ and the impurity specific heat is proportional to $T^{1/2}$ for all values of the impurity spin S. For antiferromagnetic coupling and T=0 the impurity susceptibility diverges proportionally to ‖lnH‖ as H→0 if S=(1/2, while if S>1 the impurity spin is only partially compensated for by the S=1 chain.