Emergent SU(3) symmetry in a four-leg spin tube

We consider an antiferromagnetic four-leg spin-1/2 tube using Abelian and non-Abelian bosonization. We show that in the limit of weak interchain coupling, the most relevant interaction gives rise to an emergent SU(3) symmetry, broken only by marginal interactions that can be canceled by diagonal interchain couplings. We discuss the low-energy spectrum in the semiclassical limit and using a mapping to a trimerized SU(3) spin chain. We establish that the correlation functions of ferroquadrupolar operators can be used to reveal the emergent symmetry.