Ground-State Phases of Anisotropic Mixed Diamond Chains with Spins 1 and 1/2

TL;DR

This paper explores the complex ground-state phases of anisotropic mixed spin chains with spins 1 and 1/2, revealing various magnetic and nonmagnetic phases, their phase diagrams, and observable properties through numerical and analytical methods.

Contribution

It introduces a comprehensive analysis of anisotropic mixed diamond chains, identifying new phases and providing phase diagrams with both numerical and analytical insights.

Findings

Identification of uncorrelated spin-1 cluster phases with broken translational symmetry

Discovery of Ne9el, period-doubled Ne9el, Haldane, and large-D phases

Determination of phase diagrams and low-temperature magnetic properties

Abstract

The ground-state phases of anisotropic mixed diamond chains with spins 1 and 1/2 are investigated. Both single-site and exchange anisotropies are considered. We find the phases consisting of an array of uncorrelated spin-1 clusters separated by singlet dimers. Except in the simplest case where the cluster consists of a single $S=1$ spin, this type of ground state breaks the translational symmetry spontaneously. Although the mechanism leading to this type of ground state is the same as that in the isotropic case, it is nonmagnetic or paramagnetic depending on the competition between two types of anisotropy. We also find the N\'eel, period-doubled N\'eel, Haldane, and large-$D$ phases, where the ground state is a single spin cluster of infinite size equivalent to the spin-1 Heisenberg chain with alternating anisotropies. The ground-state phase diagrams are determined for typical sets of parameters by numerical analysis. In various limiting cases, the ground-state phase diagrams are determined analytically. The low-temperature behaviors of magnetic susceptibility and entropy are investigated to distinguish each phase by observable quantities. The relationship of the present model with the anisotropic rung-alternating ladder with spin-1/2 is also discussed.