Disorder, Low-Energy Excitations, and Topology in the Kitaev Spin Liquid

Abstract

The Kitaev model is a fascinating example of an exactly solvable model displaying a spin-liquid ground state in two dimensions. However, deviations from the original Kitaev model are expected to appear in real materials. In this Letter, we investigate the fate of Kitaev's spin liquid in the presence of disorder -- bond defects or vacancies -- for an extended version of the model. Considering static flux backgrounds, we observe a power-law divergence in the low-energy limit of the density of states with a nonuniversal exponent. We link this power-law distribution of energy scales to weakly coupled droplets inside the bulk, in an uncanny similarity to the Griffiths phase often present in the vicinity of disordered quantum phase transitions. If time-reversal symmetry is broken, we find that power-law singularities are tied to the destruction of the topological phase of the Kitaev model in the presence of bond disorder alone. However, there is a transition from this topologically trivial phase with power-law singularities to a topologically nontrivial one for weak to moderate site dilution. Therefore, diluted Kitaev materials are potential candidates to host Kitaev's chiral spin-liquid phase.

Main text: 7 pages, 2 figures. Supplemental material: 8 pages, 12 figures. Published version

References in corpus (28)

• Power-law distributions in empirical data
• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Localization of interacting fermions at high temperature
• The distribution of the ratio of consecutive level spacings in random matrix ensembles
• $\alpha$-RuCl3: a Spin-Orbit Assisted Mott Insulator on a Honeycomb Lattice
• Models and Materials for Generalized Kitaev Magnetism
• Disorder Induced Localized States in Graphene
• On the Origin of Zigzag Magnetic Order in Iridium Oxide Na2IrO3
• Magnetic order in $\alpha$-RuCl${}_3$: a honeycomb lattice quantum magnet with strong spin-orbit coupling
• Rare region effects at classical, quantum, and non-equilibrium phase transitions
• Modeling disorder in graphene
• Exact results for spin dynamics and fractionization in the Kitaev Model
• Entanglement Spectrum of a Disordered Topological Chern Insulator
• Disorder-Driven Non-Fermi Liquid Behavior of Correlated Electrons
• Vaporization of Kitaev spin liquids
• Magnetization processes of zigzag states on the honeycomb lattice: Identifying spin models for $\alpha$-RuCl${}_3$ and Na${}_2$IrO${}_3$
• Quantum Griffiths effects and smeared phase transitions in metals: theory and experiment
• Disorder in a quantum spin liquid: flux binding and local moment formation
• Real-space calculation of the conductivity tensor for disordered topological matter
• Physical states and finite-size effects in Kitaev's honeycomb model: Bond disorder, spin excitations, and NMR lineshape
• Effect of nonmagnetic dilution in honeycomb lattice iridates Na${}_2$IrO${}_3$ and Li${}_2$IrO${}_3$
• Thermodynamic and Transport Properties in Disordered Kitaev Models
• Electronic Griffiths phase of the d=2 Mott transition
• Density of states in graphene with vacancies: midgap power law and frozen multifractality
• Observation of a random singlet state in a diluted Kitaev honeycomb material
• Spin dynamics in the Kitaev model with disorder: Quantum Monte Carlo study of dynamical spin structure factor, magnetic susceptibility, and NMR relaxation rate
• Valence-bond theory of highly disordered quantum antiferromagnets
• Gapless excitations in non-Abelian Kitaev spin liquids with line defects