LOCAL SUSCEPTIBILITIES IN SEMIINFINITE ANTIFERROMAGNETIC CHAINS - ELEMENTARY PERSPECTIVES

Using conformal field theory methods Eggert and Affleck [Phys. Rev. Le tt. 75, 984 (1996)] have shown that the semi-infinite S = 1/2 Heisenbe rg antiferromagnetic chain exhibits a remarkable alternation in its lo cal response to a uniform field at low temperatures. Such alternation is not an essentially quantum effect: A similar, and sometimes stronge r, susceptibility alternation is a feature of classical Heisenberg-Isi ng chains at T = 0. In S = 1/2 chains, susceptibility alternation is n ot unique to the Heisenberg model, but can be seen in expansions about the Ising model and also in the XY model.