Large-S approach to chiral phases in frustrated spin chains

Abstract

A large-S approach to the description of chiral phases in frustrated antiferromagnetic spin-S chains with easy-plane anisotropy is proposed. The approach is valid in the vicinity of the classical Lifshitz point j=1/4, where j is the relative strength of the frustrating next-nearest-neighbor coupling. The effective theory turns out to be the nonlinear sigma-model with the additional fourth-order term in spatial derivatives. The topological term persists for j>1/4, which leads to disappearance of the chiral gapped phase for half-integer S, in accordance with the recent numerical results.

uses ptptex.sty (included), 7 pages, 4 figs, to appear in Prog. Theor. Phys. Suppl. (Proc. of the 16th Nishinomiya Yukawa Memorial Symposium)