Magnetization plateaux and jumps in frustrated four-leg spin tubes in magnetic fields

H D Rosales,M Arlego,F A Gómez Albarracín

doi:10.1088/1742-6596/568/4/042023

Abstract

We study the ground state phase diagram of a frustrated spin-1/2 four-leg 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: density matrix renormalization group (DMRG), a low-energy effective Hamiltonian (LEH) and a Hartree variational approach (HVA). We find that in the limit of weakly interacting plaquettes, singlet and triplet states play an important role in the formation of 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. These results are consistent with the DMRG and HVA calculations.

Highlights

Frustrated magnetism is a subject that has attracted much attention in the last decades and magnetic frustration is the key element in the search of exotics ground states[1]
We explore the parameter space of this model in the regime of all-antiferromagnetic exchange couplings by means of three different approaches: density matrix renormalization group (DMRG), a low-energy effective Hamiltonian (LEH) and a Hartree variational approach (HVA)
We find that in the limit of weakly interacting plaquettes, singlet and triplet states play an important role in the formation of magnetization plateaux

Summary

Introduction

Frustrated magnetism is a subject that has attracted much attention in the last decades and magnetic frustration is the key element in the search of exotics ground states[1]. In the last years there has been a growing interest to the phenomenon of magnetization plateaux in quasi one-dimensional spin systems, comprising chain, ladder and more involved magnetic structures spin systems. In a variety of models, the magnetization as a function of the applied magnetic field h exhibits plateaus at certain values; at those plateaux the magnetization in units of the saturation m = M/Ms is locked at some rational number. Cu2Cl4·D8C4SO2 has been established as a new spin 1/2 tube with an even number of legs [3] with diagonal coupling between adjacent legs. 1 2 tube with a geometry depicted in Fig. 1 in a magnetic field and described by the following Hamiltonian:. For J1,2 J0, the quantum properties of the frustrated four spin tube can be understood in terms of weakly coupled four-spin plaquettes.

Low Energy Models

DMRG analysis

Conclusion