Two-step gap opening across the quantum critical point in a Kitaev honeycomb magnet

Abstract

Quantum spin liquid involves fractionalized quasipariticles such as spinons and visons. They are expressed as itinerant Majorana fermions and $Z_2$ fluxes in the Kitaev model with bond-dependent exchange interactions on a honeycomb spin lattice. The observation has recently attracted attention for a candidate material $\alpha$-RuCl${}_3$, showing spin liquid behaviour induced by a magnetic field. Since the observable spin excitation is inherently composed of the two quasiparticles, which further admix each other by setting in the magnetic field as well as non-Kitaev interactions, their individual identification remains challenging. Here we report an emergent low-lying spin excitation through nuclear magnetic and quadrupole resonance measurements down to $\sim 0.4$ K corresponding to $1/500$ of the exchange energy under the finely tuned magnetic field across the quantum critical point. We determined the critical behaviour of low-lying excitations and found evolution of two kinds of the spin gap at high fields. The two excitations exhibit repulsive magnetic field dependence, suggesting anti-crossing due to the hybridization between fractionalized quasiparticles.

arXiv comment5 pages, 4 figures

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Cited by in corpus (27)

• Thermodynamic and Transport Properties in Disordered Kitaev Models
• Magnetism of Kitaev spin-liquid candidate material RuBr${}_3$
• Origin of oscillatory structures in the magnetothermal conductivity of the putative Kitaev magnet $\alpha$-RuCl${}_3$
• Majorana-fermion origin of the planar thermal Hall effect in the Kitaev magnet $\alpha$-RuCl${}_3$
• Strongly electron-correlated semimetal RuI${}_3$ with a layered honeycomb structure
• Symmetry-based requirement for the measurement of electrical and thermal Hall conductivity under an in-plane magnetic field
• Kitaev Quantum Spin Liquids
• Spin dynamics in the Kitaev model with disorder: Quantum Monte Carlo study of dynamical spin structure factor, magnetic susceptibility, and NMR relaxation rate
• Magnetic phase diagram and possible Kitaev-like behavior of honeycomb-lattice antimonate Na3Co2SbO6
• Majorana-Magnon Crossover by a Magnetic Field in the Kitaev Model: Continuous-Time Quantum Monte Carlo Study
• Field-angle dependence of thermal Hall conductivity in magnetically ordered Kitaev-Heisenberg system
• NMR Investigation on Honeycomb Iridate Ag${}_3$LiIr${}_2$O${}_6$
• Field evolution of magnetic phases and spin dynamics in the honeycomb lattice magnet Na2Co2TeO6: 23Na NMR study
• Defect-Induced Low-Energy Majorana Excitations in the Kitaev Magnet $\alpha$-RuCl${}_3$
• Two-step growth of high-quality single crystals of the Kitaev magnet $\alpha$-RuCl${}_3$
• Neutron spectroscopy evidence for a possible magnetic-field-induced gapless quantum-spin-liquid phase in a Kitaev material $\alpha$-RuCl${}_3$
• Light-induced magnetization driven by interorbital charge motion in a spin-orbit assisted Mott insulator alpha-RuCl3
• $J=1/2$ Pseudospins and $d$-$p$ Hybridization in the Kitaev Spin Liquid Candidates Ru$X_3$ ($X$ = Cl, Br, I)
• Asymmetric modulation of Majorana excitation spectra and nonreciprocal thermal transport in the Kitaev spin liquid under a staggered magnetic field
• Spin Seebeck Effect as a Probe for Majorana Fermions in Kitaev Spin Liquids
• Gapless excitations in non-Abelian Kitaev spin liquids with line defects
• Dimensional reduction of Kitaev spin liquid at quantum criticality
• Signatures of a gapless quantum spin liquid in the Kitaev material Na${}_3$Co${}_{2-x}$Zn${}_x$SbO${}_6$
• Field tuning Kitaev systems for spin fractionalization and topological order
• Coupled spin-1/2 antiferromagnetic chain Cs${}_2$LiRuCl${}_6$ with partially disordered crystal lattice
• A quantum Monte Carlo method on asymptotic Lefschetz thimbles for quantum spin systems: An application to the Kitaev model in a magnetic field
• Ground state of the staggered Heisenberg-$\Gamma$ honeycomb model in a magnetic field