Haldane Phases and Ferrimagnetic Phases with Spontaneous Translational Symmetry Breakdown in Distorted Mixed Diamond Chains with Spins 1 and 1/2

TL;DR

This paper explores how lattice distortions in mixed diamond chains with spins 1 and 1/2 induce various quantum phases, including Haldane and ferrimagnetic phases, with detailed analysis of symmetry breaking and phase transitions.

Contribution

It introduces a comprehensive analysis of distorted mixed diamond chains, revealing the emergence of Haldane and ferrimagnetic phases with spontaneous symmetry breaking and classifying phase transitions.

Findings

Distorted chains exhibit Haldane phases with or without STSB.

Effective interactions determine the emergence of ferrimagnetic phases.

Transitions follow the universality class of the $(n+1)$-clock model.

Abstract

The ground states of two types of distorted mixed diamond chains with spins 1 and 1/2 are investigated using exact diagonalization, DMRG, and mapping onto low-energy effective models. In the undistorted case, the ground state consists of an array of independent spin-1 clusters separated by singlet dimers. The lattice distortion induces an effective interaction between cluster spins. When this effective interaction is antiferromagnetic, several Haldane phases appear with or without spontaneous translational symmetry breakdown (STSB). The transition between the Haldane phase without STSB and that with $(n+1)$-fold STSB ($n$ = 1, 2, and 3) belongs to the same universality class as the $(n+1)$-clock model. In contrast, when the effective interaction is ferromagnetic, the quantized and partial ferrimagnetic phases appear with or without STSB. An effective low-energy theory for the partial ferrimagnetic phase is presented.