Two-leg SU(2n) spin ladder: A low-energy effective field theory approach

TL;DR

This paper analyzes a two-leg SU(2n) spin ladder model using field theory, revealing a phase diagram with generalized Valence Bond Solid phases and a cluster phase relevant to ultracold ytterbium atoms with emergent SU(6) symmetry.

Contribution

It provides a low-energy effective field theory description of two-leg SU(2n) spin ladders, identifying novel phases and their properties, especially for n>1.

Findings

No topological phases for n>1 in the phase diagram.

Existence of generalized Valence Bond Solid phases with different wave vectors.

Identification of a cluster phase relevant to ultracold ytterbium atoms.

Abstract

We present a field theory analysis of a model of two SU(2n)-invariant magnetic chains coupled by a generic interaction preserving time reversal and inversion symmetry. Contrary to the SU(2)-invariant case the zero-temperature phase diagram of such two-leg spin ladder does not contain topological phases. Only generalized Valence Bond Solid phases are stabilized when n>1 with different wave vectors and ground-state degeneracies. In particular, we find a phase which is made of a cluster of 2n spins put in an SU(2n) singlet state. For n=3, this cluster phase is relevant to ytterbium ultracold atoms, with an emergent SU(6) symmetry, loaded in double well optical lattice.