Non-Landau quantum phase transition in modulated SU(N) Heisenberg spin chains

TL;DR

This paper explores a unique non-Landau quantum phase transition in modulated SU(N) Heisenberg spin chains, revealing a transition to a topological phase with fractionalized excitations governed by SU(N)$_1$ conformal field theory.

Contribution

It demonstrates a non-Landau phase transition in one-dimensional SU(N) spin chains, characterized by a topological SPT phase and governed by SU(N)$_1$ conformal field theory, distinct from traditional symmetry-breaking transitions.

Findings

Transition separates trivial and topological SPT phases.

Transition is governed by edge state delocalization, not Ising symmetry breaking.

Fractionalized spinon excitations are present in the SPT phase.

Abstract

We investigate the nature of the quantum phase transition in modulated SU(N) Heisenberg spin chains. In the odd-N case, the transition separates a trivial non-degenerate phase to a doubly-degenerate gapped chiral PSU(N) symmetry-protected topological (SPT) phase which breaks spontaneously the inversion symmetry. The transition is not an Ising transition associated to the breaking of the $\mathbb{Z}_2$ inversion symmetry, but is governed by the delocalization of the edge states of the SPT phase. In this respect, a modulated SU(N) Heisenberg spin chain provides a simple example in one dimension of a non-Landau phase transition which is described by the SU(N)$_1$ conformal field theory. We show that the chiral SPT phase exhibits fractionalized spinon excitations, which can be confined by changing the model parameters slightly.