The phase diagram of the anisotropic spin-2 XXZ model: an infinite system DMRG study

TL;DR

This paper uses an advanced numerical method to map out the phase diagram of the quantum spin-2 XXZ chain with anisotropy, revealing connections to the spin-1 Haldane phase and classical limits.

Contribution

It demonstrates the application of iDMRG to analyze the phase diagram of the spin-2 XXZ model, establishing connections to the spin-1 Haldane phase and classical phases.

Findings

Spin-2 model can realize a topologically nontrivial Haldane phase.

The spin-2 Haldane phase is connected to the large-D phase without phase transition.

Methodology for using iDMRG to explore complex quantum spin chains.

Abstract

We study the ground state phase diagram of the quantum spin-2 XXZ chain in the presence of on-site anisotropy using a matrix-product state based infinite system density-matrix-renormalization-group (iDMRG) algorithm. One of the interests in this system is in connecting the highly quantum mechanical spin-1 phase diagram with the classical S=infinity phase diagram. Several of the recent advances within DMRG make it possible to perform a detailed analysis of the whole phase diagram. We consider different types of on-site anisotropies which allows us to establish the validity of the following statements: One, the spin-2 model can be tuned into a phase which is equivalent to the "topologically nontrivial" spin-1 Haldane phase. Two, the spin-2 Haldane phase at the isotropic Heisenberg point is adiabatically connected to the "trivial" large-D phase, with a continuous change of the Hamiltonian parameters. Furthermore, we study the spin-3 XXZ chain to help explain the development of the classical phase diagram. We present details on how to use the iDMRG method to map out the phase diagram and include an extensive discussion of the numerical methods.