Phases and phase transitions of a perturbed Kekulé-Kitaev model

Abstract

We study the quantum spin liquid phase in a variant of the Kitaev model where the bonds of the honeycomb lattice are distributed in a Kekulé pattern. The system supports gapped and gapless Z_2 quantum spin liquids with interesting differences from the original Kitaev model, the most notable being a gapped Z_2 spin liquid on a Kagome lattice. Perturbing the exactly solvable model with antiferromagnetic Heisenberg perturbations, we find a magnetically ordered phase stabilized by a quantum `order by disorder' mechanism, as well as an exotic continuous phase transition between the topological spin liquid and this magnetically ordered phase. Using a combination of field theory and Monte-Carlo simulations, we find that the transition likely belongs to the 3D-XYxZ_2 universality class.

15 pages, 11 figures

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• On Topology of the Moduli Space of Gapped Hamiltonians for Topological Phases
• Bound states of fractionalized excitations in a modulated Kitaev spin liquid
• A primer on Kitaev Model: Basic aspects, material realization, and recent experiments
• Valence-Bond Solid phases in the spin-$1/2$ Kekule-Heisenberg model
• The Kekulé-Kitaev model: linear and non-linear responses and magnetic field effects
• Phases and Quantum Phase Transitions in Anisotropic Antiferromagnetic Kitaev-Heisenberg-$\Gamma$ magnet