Quantum Phase Transitions in Alternating-Bond Mixed Diamond Chains with Spins 1 and 1/2

TL;DR

This paper explores how alternating exchange interactions in mixed spin diamond chains lead to diverse ground states and an infinite series of quantum phase transitions, revealing complex magnetic behavior.

Contribution

It introduces a detailed phase diagram for mixed spin chains with alternating bonds and uncovers an infinite series of quantum phase transitions for strong distortion.

Findings

Multiple ground states depending on frustration and distortion

Infinite series of quantum phase transitions identified

Steps in Curie constant and residual entropy observed

Abstract

We investigate the mixed diamond chain composed of spins 1 and 1/2 when the exchange interaction is alternatingly distorted. Depending on the strengths of frustration and distortion, this system has various ground states. Each ground state consists of an array of spin clusters separated by singlet dimers by virtue of an infinite number of local conservation laws. We determine the ground state phase diagram by numerically analyzing each spin cluster. In particular for strong distortion, we find an infinite series of quantum phase transitions by the cluster expansion method and conformal field theory. This leads to the infinite series of steps in the behavior of the Curie constant and residual entropy.