Topological to magnetically ordered quantum phase transition in antiferromagnetic spin ladders with long-range interactions

TL;DR

This paper investigates a quantum spin ladder with long-range interactions, revealing a second-order phase transition from a non-local string ordered phase to a Ne9el ordered phase, with detailed spectral analysis and potential deconfined criticality.

Contribution

The study demonstrates a continuous quantum phase transition in a long-range interacting spin ladder using QMC and DMRG, highlighting the evolution of excitations and the possibility of deconfined criticality.

Findings

Transition from string order to Ne9el order is second order.

Gapless modes appear in the ordered phase, gapped excitations are triplons.

Triplon band evolves into a gapless magnon dispersion.

Abstract

We study a generalized quantum spin ladder with staggered long range interactions that decay as a power-law with exponent $\alpha$. Using large scale quantum Monte Carlo (QMC) and the density matrix renormalization group (DMRG) simulations, we show that this model undergoes a transition from a rung-dimer phase characterized by a non-local string order parameter, to a symmetry broken N\'eel phase. We find evidence that the transition is second order.In the magnetically ordered phase, the spectrum exhibits gapless modes, while excitations in the gapped phase are well described in terms of triplons -- bound states of spinons across the legs. We obtain the momentum resolved spin dynamic structure factor numerically and find a well defined triplon band evolves into a gapless magnon dispersion through the transition. We further discuss the possibility of deconfined criticality in this model.