Heisenberg-Ising delta-chain with bond alternation

TL;DR

This paper investigates the ground state properties of a spin-1/2 delta-chain with bond alternation, revealing a phase diagram with magnetic and non-magnetic gapped phases using exact diagonalization and DMRG methods.

Contribution

It provides a detailed analysis of the phase diagram of the Heisenberg-Ising delta-chain with bond alternation, including the origin of energy gaps.

Findings

Identification of magnetic and non-magnetic phases

All phases except ferrimagnetic are gapped

Clarification of the origin of the energy gaps

Abstract

The spin-$\frac{1}{2}$ delta-chain (sawtooth chain) with antiferromagnetic Heisenberg basal chain and Ising apical-basal interactions is studied. The basal-apical interactions involve the bond alternation. The limiting cases of the model include the symmetrical delta-chain and the antiferromagnetic chain in the staggered magnetic field. We study ground state properties of the model by the exact diagonalization and density matrix renormalization group methods. The ground state phase diagram as a function of the bond alternation consists of magnetic and various non-magnetic phases. All phases excluding the ferrimagnetic phase are gapped and an origin of the gaps is cleared.