Finite Temperature Properties of the Mixed Diamond Chain with Spins 1 and 1/2

TL;DR

This paper develops a statistical mechanics framework for a mixed spin diamond chain, revealing quantum phase transitions and complex finite-temperature magnetic properties driven by frustration.

Contribution

It introduces a novel approach leveraging conservation laws to analyze finite-temperature behavior of mixed spin chains with multiple quantum phases.

Findings

Identification of five quantum phase transitions as frustration varies

Characterization of residual entropy and Curie constant in different phases

Observation of nonmonotonic susceptibility and multipeak specific heat structures

Abstract

We formulate statistical mechanics for the mixed diamond chain with spins of magnitudes 1 and 1/2. Owing to a series of conservation laws, any eigenstate of this system is decomposed into eigenstates of finite odd-length spin-1 chains. The ground state undergoes five quantum phase transitions with varying the parameter $\lambda$ controlling frustration. We obtain the values of the residual entropy and the Curie constant which characterize each phase and phase boundary at low temperatures. We further find various characteristic finite-temperature properties such as the nonmonotonic temperature dependence of the magnetic susceptibility, the multipeak structure in the $\lambda$-dependence of entropy, the plateau-like temperature dependence of entropy and the multipeak structure of specific heat.