SU(N) Evolution of a Frustrated Spin Ladder

TL;DR

This paper explores the SU(N) generalization of frustrated spin ladders, revealing how spinon excitations and dynamical structure factors evolve with N, and highlighting non-trivial behaviors at large N.

Contribution

It provides a detailed analysis of the SU(N) spin ladder, showing the differences in dynamical structure factors and the non-trivial large N limit, extending understanding beyond the SU(2) case.

Findings

Spinons are stabilized by frustration across SU(N) models.

Dynamical structure factors differ qualitatively between N=2 and N>2.

The large N limit of the four-chain magnet is non-trivial and not free.

Abstract

Recent studies indicate that the weakly coupled spin-1/2 Heisenberg antiferromagnet with next nearest neighbor frustration supports massive spinons when suitably tuned. The straightforward SU(N) generalization of the low energy ladder Hamiltonian yields two independent SU(N) Thirring models with N-1 multiplets of massive ``spinon'' excitations. We study the evolution of the complete set of low-energy dynamical structure factors using form factors. Those corresponding to the smooth (staggered) magnetizations are qualitatively different (the same) in the N=2 and N>2 cases. The absence of single-particle peaks preserves the notion of spinons stabilized by frustration. In contrast to the ladder, we note that the N=infinity limit of the four chain magnet is not a trivial free theory.