Magnetization plateaux and jumps in a frustrated four-leg spin tube under a magnetic field

TL;DR

This paper investigates the complex magnetic phases of a frustrated four-leg spin tube under an external magnetic field, revealing fractional magnetization plateaux through multiple analytical and numerical methods.

Contribution

It introduces a comprehensive analysis combining effective Hamiltonian, variational, and DMRG methods to identify fractional magnetization plateaux in the model.

Findings

Identification of fractional magnetization plateaux.

Agreement among different analytical and numerical approaches.

Prediction of plateaux existence in specific parameter regions.

Abstract

We study the ground state phase diagram of a frustrated spin-1/2 four-leg spin tube in an external magnetic field. We explore the parameter space of this model in the regime of all-antiferromagnetic exchange couplings by means of three different approaches: analysis of low-energy effective Hamiltonian (LEH), a Hartree variational approach (HVA) and density matrix renormalization group (DMRG) for finite clusters. We find that in the limit of weakly interacting plaquettes, low-energy singlet, triplet and quintuplet states play an important role in the formation of fractional magnetization plateaux. We study the transition regions numerically and analytically, and find that they are described, at first order in a strong- coupling expansion, by an XXZ spin-1/2 chain in a magnetic field; the second-order terms give corrections to the XXZ model. All techniques provide consistent results which allow us to predict the existence of fractional plateaux in an important region in the space of parameters of the model.