Quantum Phase Diagram of the Bilayer Kitaev-Heisenberg Model

TL;DR

This study maps the complex ground-state phase diagram of the bilayer Kitaev-Heisenberg model, revealing multiple magnetic and quantum spin liquid phases, and emphasizes the role of interlayer interactions in quantum phase emergence.

Contribution

It provides the first large-scale tensor network analysis of the bilayer Kitaev-Heisenberg model, uncovering new quantum phases like the valence bond solid.

Findings

Identification of two quantum spin liquid phases near the Kitaev limit

Discovery of a valence bond solid phase between AFM and stripy states

Interlayer interactions significantly influence quantum phase stability

Abstract

We study the ground-state phase diagram of the spin-$1/2$ Kitaev-Heisenberg model on the bilayer honeycomb lattice with large-scale tensor network calculations based on the infinite projected entangled pair state technique as well as high-order series expansions. We find that beyond various magnetically ordered phases, including ferromagnetic, zigzag, antiferromagnetic (AFM) and stripy states, two extended quantum spin liquid phases arise in the proximity of the Kitaev limit. While these ordered phases also appear in the monolayer Kitaev-Heisenberg model, our results further show that a valence bond solid state emerges in a relatively narrow range of parameter space between the AFM and stripy phases, which can be adiabatically connected to isolated Heisenberg dimers. Our results highlight the importance of considering interlayer interactions on the emergence of novel quantum phases in the bilayer Kitaev materials.