The fate of spinons in spontaneously dimerised spin-1/2 ladders

TL;DR

This paper investigates how spinons, elementary excitations in a frustrated spin-1/2 ladder, persist as gapped excitations despite a transition to a dimerised ground state due to weak interchain coupling.

Contribution

It demonstrates that spinons survive as elementary excitations in a dimerised phase, with an exact calculation of the dynamical structure factor for various momenta.

Findings

Spinons remain as elementary excitations in the dimerised phase.

The ground state becomes spontaneously dimerised due to weak interchain coupling.

The dynamical structure factor is exactly determined for multiple momentum values.

Abstract

We study a weakly coupled, frustrated two-leg spin-1/2 Heisenberg ladder. For vanishing coupling between the chains, elementary excitations are deconfined, gapless spin-1/2 objects called spinons. We investigate the fate of spinons for the case of a weak interchain interaction. We show that despite a drastic change in ground state, which becomes spontaneously dimerised, spinons survive as elementary excitations but acquire a spectral gap. We furthermore determine the exact dynamical structure factor for several values of momentum transfer.