Ising phases of Heisenberg ladders in a magnetic field

TL;DR

This paper investigates how weak anisotropic interactions, especially Dzyaloshinskii--Moriya coupling, alter the phase diagram of frustrated two-leg Heisenberg ladders, revealing merged magnetization plateaux and new Ising-ordered phases.

Contribution

It demonstrates that weak anisotropic interactions can significantly modify the phase diagram of frustrated Heisenberg ladders, introducing new Ising-ordered phases and merging magnetization plateaux.

Findings

Dzyaloshinskii--Moriya coupling merges half-integer plateau with gapless phases.

Different Ising order identified in weakly frustrated ladders.

Implications for experimental ladder and dimer systems discussed.

Abstract

We examine the influence of weak anisotropic interactions on the T=0 phase diagram of the frustrated two-leg Heisenberg ladder, a well-studied spin model exhibiting integer and fractional magnetization plateaux separated by gapless incommensurate states. We find that the Dzyaloshinskii--Moriya coupling may substantially modify the phase diagram so that the half-integer plateau and the surrounding gapless phases merge into a single Ising-ordered phase breaking the translational symmetry of the lattice. A different Ising order is found for a weakly frustrated ladder. Implications for experimental ladder and dimer systems are discussed.