Breathers and Raman scattering in a two-leg ladder with staggered Dzialoshinskii-Moriya interaction

TL;DR

This paper develops an effective field theory for a two-leg ladder with staggered Dzialoshinskii-Moriya interaction, predicting persistent spin gaps and bound states observable via Raman scattering, extending understanding of magnetic excitations.

Contribution

It introduces a low energy effective field theory for a magnetized two-leg ladder with weak staggered Dzialoshinskii-Moriya interaction, highlighting novel spectral features.

Findings

Persistence of the spin gap in the magnetized phase

Presence of bound states in the excitation spectrum

Observable Raman scattering signatures

Abstract

Recent experiments have revealed the role of staggered Dzialoshinskii-Moriya interaction in the magnetized phase of an antiferromagnetic spin 1/2 two-leg ladder compound under a uniform magnetic field. We derive a low energy effective field theory describing a magnetized two-leg ladder with a weak staggered Dzialoshinskii-Moriya interaction. This theory predicts the persistence of the spin gap in the magnetized phase, in contrast to standard two-leg ladders, and the presence of bound states in the excitation spectrum. Such bound states are observable in Raman scattering measurements. These results are then extended to intermediate Dzialoshinskii-Moriya interaction using Exact Diagonalizations.