Vacancy-induced low-energy density of states in the Kitaev spin liquid

Abstract

The Kitaev honeycomb model has attracted significant attention due to its exactly solvable spin-liquid ground state with fractionalized Majorana excitations and its possible materialization in magnetic Mott insulators with strong spin-orbit couplings. Recently, the 5d-electron compound H${}_3$LiIr${}_2$O${}_6$ has shown to be a strong candidate for Kitaev physics considering the absence of any signs of a long-range ordered magnetic state. In this work, we demonstrate that a finite density of random vacancies in the Kitaev model gives rise to a striking pileup of low-energy Majorana eigenmodes and reproduces the apparent power-law upturn in the specific heat measurements of H${}_3$LiIr${}_2$O${}_6$. Physically, the vacancies can originate from various sources such as missing magnetic moments or the presence of non-magnetic impurities (true vacancies), or from local weak couplings of magnetic moments due to strong but rare bond randomness (quasivacancies). We show numerically that the vacancy effect is readily detectable even at low vacancy concentrations and that it is not very sensitive neither to nature of vacancies nor to different flux backgrounds. We also study the response of the site-diluted Kitaev spin liquid to the three-spin interaction term, which breaks time-reversal symmetry and imitates an external magnetic field. We propose a field-induced flux-sector transition where the ground state becomes flux free for larger fields, resulting in a clear suppression of the low temperature specific heat. Finally, we discuss the effect of dangling Majorana fermions in the case of true vacancies and show that their coupling to an applied magnetic field via the Zeeman interaction can also account for the scaling behavior in the high-field limit observed in H${}_3$LiIr${}_2$O${}_6$.

14 pages, 13 figures

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Cited by in corpus (43)

• Dynamics of visons and thermal Hall effect in perturbed Kitaev models
• Variational study of the Kitaev-Heisenberg-Gamma model
• Effect of structural disorder on the Kitaev magnet Ag${}_3$LiIr${}_2$O${}_6$
• Kitaev Quantum Spin Liquids
• Scanning tunneling spectroscopy of Majorana zero modes in a Kitaev spin liquid
• Spin dynamics in the Kitaev model with disorder: Quantum Monte Carlo study of dynamical spin structure factor, magnetic susceptibility, and NMR relaxation rate
• Non-local spin correlation as a signature of Ising anyons trapped in vacancies of the Kitaev spin liquid
• Complex pressure-temperature structural phase diagram of honeycomb iridate Cu${}_2$IrO${}_3$
• Emergent moments and random singlet physics in a Majorana spin liquid
• Thermal anyon interferometry in phonon-coupled Kitaev spin liquids
• Instabilities of spin-1 Kitaev spin liquid phase in presence of single-ion anisotropies
• Analytic calculation of the vison gap in the Kitaev spin liquid
• Majorana correlations in the Kitaev model with ordered-flux structures
• Dynamical anyon generation in Kitaev honeycomb non-Abelian spin liquids
• Defect-Induced Low-Energy Majorana Excitations in the Kitaev Magnet $\alpha$-RuCl${}_3$
• Exceptional dynamics of interacting spin liquids
• Disorder effects in the Kitaev-Heisenberg model
• Quantum paramagnetism in the hyperhoneycomb Kitaev magnet $\beta$-ZnIrO${}_3$
• Spin- and Flux-gap Renormalization in the Random Kitaev Spin Ladder
• Suppression of the antiferromagnetic order by Zn doping in a possible Kitaev material Na${}_2$Co${}_2$TeO${}_6$
• Disorder-induced excitation continuum in a spin-1/2 cobaltate on a triangular lattice
• Gapless excitations in non-Abelian Kitaev spin liquids with line defects
• Role of disorder in the electronic and magnetic properties of Ag${}_3$LiIr${}_2$O${}_6$
• Spin Seebeck Effect as a Probe for Majorana Fermions in Kitaev Spin Liquids
• High-temperature magnetic anomaly via suppression of antisite disorder through synthesis route modification in a Kitaev candidate Cu${}_2$IrO${}_3$
• Signatures of a gapless quantum spin liquid in the Kitaev material Na${}_3$Co${}_{2-x}$Zn${}_x$SbO${}_6$
• Quasicrystalline Spin Liquid
• Dilution of the magnetic lattice in the Kitaev candidate $\alpha$-RuCl${}_3$ by Rh${}^{3+}$ doping
• Static and dynamical magnetic properties of the extended Kitaev-Heisenberg model with spin vacancies
• Bulk excitations in ultraclean $\alpha$-RuCl${}_3$: Quantitative evidence for Majorana dispersions in a Kitaev quantum spin liquid
• Quantum computation at the edge of a disordered Kitaev honeycomb lattice
• Topological Majorana flat bands in the Kitaev model on a Bishamon-kikko lattice
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• Majorana Signatures in Planar Tunneling through a Kitaev Spin Liquid
• Tunable anyonic permeability across ${\mathbb{Z}}_2$ spin liquid junctions
• Disorder, Low-Energy Excitations, and Topology in the Kitaev Spin Liquid
• Designing atomic-scale resistive circuits in topological insulators through vacancy-induced localized modes
• Fractional Wannier Orbitals and Tight-Binding Gauge Fields for Kitaev Honeycomb Superlattices with Flat Majorana Bands