Hole propagation in the Kitaev-Heisenberg model: From quasiparticles in quantum Neel states to non-Fermi liquid in the Kitaev phase

Abstract

We explore with exact diagonalization the propagation of a single hole in four magnetic phases of the t-J-like Kitaev-Heisenberg model on a honeycomb lattice: the Neel antiferromagnetic, stripe, zigzag and Kitaev spin-liquid phase. We find coherent propagation of spin-polaron quasiparticles in the antiferromagnetic phase by a similar mechanism as in the $t$-$J$ model for high-$T_c$ cuprates. In the stripe and zigzag phases clear quasiparticles features appear in spectral functions of those propagators where holes are created and annihilated on one sublattice, while they remain largely {\it hidden} in those spectral functions that correspond to photoemission experiments. As the most surprising result, we find a totally incoherent spectral weight distribution for the spectral function of a hole moving in the Kitaev spin-liquid phase in the strong coupling regime relevant for iridates. At intermediate coupling the finite systems calculation reveals a well defined quasiparticle at the $\Gamma$ point, however, we find that the gapless spin excitations wipe out quasiparticles at finite momenta. Also for this more subtle case we conclude that in the thermodynamic limit the lightly doped Kitaev liquid phase does not support quasiparticle states in the neighborhood of $\Gamma$, and therefore yields a {\it non-Fermi liquid}, contrary to earlier suggestions based on slave-boson studies. These observations are supported by the presented study of the dynamic spin-structure factor for the Kitaev spin liquid regime.

10 pages, 8 figures

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• Three dimensional quantum spin liquids in models of harmonic-honeycomb iridates and phase diagram in an infinite-D approximation
• Phase diagram and spin correlations of the Kitaev-Heisenberg model: Importance of quantum effects
• Kitaev-like honeycomb magnets: Global phase behavior and emergent effective models
• Destabilization of magnetic order in a dilute Kitaev spin liquid candidate
• Doping a topological quantum spin liquid: slow holes in the Kitaev honeycomb model
• Fractons from polarons
• Spectral function and fidelity susceptibility in quantum critical phenomena
• Quantum Walk in Degenerate Spin Environments
• Frustration and Entanglement in Compass and Spin-Orbital Models
• Hydrated lithium intercalation into the Kitaev spin liquid candidate material $\alpha -$RuCl${}_3$
• Anomalous spin-charge separation in a driven Hubbard system
• Coherent hole propagation in an exactly solvable gapless spin liquid
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• Correlations generated from high-temperature states: nonequilibrium dynamics in the Fermi-Hubbard model
• Pairing tendencies in the doped Kitaev-Heisenberg model
• Spectrum of the hole excitation in spin-orbit Mott insulator Na${}_2$IrO${}_3$