Magnetic excitations in magnetization plateaux of a frustrated spin ladder

TL;DR

This paper investigates magnetic excitations in magnetization-plateau phases of a frustrated spin ladder, revealing a reconstructed quasi-particle called trimeron arising from broken translational symmetry, using numerical and analytical methods.

Contribution

It provides the first detailed analysis of the microscopic mechanism behind reconstructed quasi-particles in magnetization-plateau phases of frustrated spin ladders.

Findings

Identification of a collective mode called trimeron.

Evidence of reconstructed quasi-particle from broken symmetry.

Agreement between numerical and analytical results.

Abstract

Magnetization plateaux emerging in quantum spin systems due to spontaneously breaking of translational symmetry have been reported both theoretically and experimentally. The broken symmetry can induce reconstruction of elementary excitations such as Goldstone and Higgs modes, whereas its microscopic mechanism and reconstructed quasi-particle in magnetization-plateau phases have remained unclear so far. Here we theoretically study magnetic excitations in the magnetization-plateau phases of a frustrated spin ladder by using dynamical density-matrix renormalization-group method. Additionally, analytical approaches with perturbation theory are performed to obtain intuitive view of magnetic excitations. Comparison between numerical and analytical results indicates the presence of a reconstructed quasi-particle originating from spontaneously broken translational symmetry, which is realized as a collective mode of spin trimer called trimeron.