Majorana-Magnon Crossover by a Magnetic Field in the Kitaev Model: Continuous-Time Quantum Monte Carlo Study

Abstract

Kitaev quantum spin liquids host Majorana fermions via the fractionalization of spins. In a magnetic field, the Majorana fermions were predicted to comprise a topological state, which has attracted great attention by the discovery of the half-quantized thermal Hall conductivity. Nevertheless, a reliable theory remains elusive for the field effect, especially at finite temperature. Here we present unbiased large-scale numerical results for the Kitaev model in a wide range of magnetic field and temperature. We find that the unconventional paramagnetic region showing fractional spin dynamics extends at finite temperature, far beyond the field range where the topological state is expected at zero temperature. Our results show the confinement-deconfinement behavior between the fractional Majorana excitations and the conventional magnons.

arXiv comment6 pages, 4 figures, accepter for the publication in Physical Review B: Rapid Communications

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• Thermodynamic and Transport Properties in Disordered Kitaev Models
• Theory of the Kitaev model in a [111] magnetic field
• Scale-invariant magnetic anisotropy in RuCl${}_3$ at high magnetic fields
• Kitaev Quantum Spin Liquids
• Universal Thermodynamics in the Kitaev Fractional Liquid
• Spin dynamics in the Kitaev model with disorder: Quantum Monte Carlo study of dynamical spin structure factor, magnetic susceptibility, and NMR relaxation rate
• Evidence for the first-order topological phase transition in a Kitaev spin liquid candidate $\alpha$-RuCl${}_3$
• Field-angle dependence of thermal Hall conductivity in magnetically ordered Kitaev-Heisenberg system
• Magnetoelectric generation of a Majorana-Fermi surface in Kitaev's honeycomb model
• Flavor-wave theory with quasiparticle damping at finite temperatures: Application to chiral edge modes in the Kitaev model
• Flux mobility delocalization in the Kitaev spin ladder
• Update of $\mathcal{H}\Phi$: Newly added functions and methods in versions 2 and 3
• Spin excitation continuum to topological magnon crossover and thermal Hall conductivity in Kitaev magnets
• Dynamics of fractionalized mean-field theories: consequences for Kitaev materials
• Asymmetric modulation of Majorana excitation spectra and nonreciprocal thermal transport in the Kitaev spin liquid under a staggered magnetic field
• Disentangling spin excitation continua in classical and quantum magnets using 2D nonlinear spectroscopy
• High-field quantum spin liquid transitions and angle-field phase diagram of Kitaev magnet $\alpha$-RuCl${}_3$
• Digital Quantum Simulation of the Kitaev Quantum Spin Liquid