The Role of the Third Dimension in Searching Majorana Fermions in $\alpha$-RuCl${}_3$ via Phonons

Abstract

Understanding phonons in $\alpha$-RuCl${}_3$ is critical to analyze the controversy around the observation of the half-integer thermal quantum Hall effect. While many studies have focused on the magnetic excitations in $\alpha$-RuCl${}_3$, its vibrational excitation spectrum has remained relatively unexplored. We investigate the phonon structure of $\alpha$-RuCl${}_3$ via inelastic neutron scattering experiments and density functional theory calculations. Our results show excellent agreement between experiment and first principles calculations. After validating our theoretical model, we extrapolate the low energy phonon properties. We find that the phonons in $\alpha$-RuCl${}_3$ that either propagate or vibrate in the out-of-plane direction have significantly reduced velocities, and therefore have the potential to dominate the observability of the elusive half integer plateaus in the thermal Hall conductance. In addition, we use low-energy interlayer phonons to resolve the low temperature stacking structure of our large crystal of $\alpha$-RuCl${}_3$, which we find to be consistent with that of the $R\bar{3}$ space group, in agreement with neutron diffraction.

arXiv commentThe first two authors contributed equally

References in corpus (39)

• Fault-tolerant quantum computation by anyons
• Non-Abelian Anyons and Topological Quantum Computation
• Anyons in an exactly solved model and beyond
• A linear response approach to the calculation of the effective interaction parameters in the LDA+U method
• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Kitaev-Heisenberg Model on Honeycomb Lattice: Possible Exotic Phases in Iridium Oxides $A_2$IrO${}_3$
• Proximate Kitaev Quantum Spin Liquid Behaviour in α-RuCl${}_3$
• Spin waves and revised crystal structure of honeycomb iridate Na2IrO3
• Challenges in Design of Kitaev Materials: Magnetic Interactions from Competing Energy Scales
• The monoclinic crystal structure of $\alpha$-RuCl${}_3$ and the zigzag antiferromagnetic ground state
• Scattering Continuum and Possible Fractionalized Excitations in $\alpha$-RuCl${}_3$
• Low-temperature crystal and magnetic structure of $\alpha$-RuCl3
• Direct evidence of a zigzag spin chain structure in the honeycomb lattice: A neutron and x-ray diffraction investigation on single crystal $\mathrm{N}{\mathrm{a}}_2\mathrm{Ir}{\mathrm{O}}_3$
• Evidence for a Field-induced Quantum Spin Liquid in $\alpha$-RuCl${}_3$
• Long range magnetic ordering in Na${}_2$IrO${}_3$
• Successive magnetic phase transitions in $\mathbf{\alpha }$-RuCl${}_3$: XY-like frustrated magnet on the honeycomb lattice
• Fundamental Spin Interactions Underlying the Magnetic Anisotropy in the Kitaev Ferromagnet CrI${}_3$
• Magnetic Excitations and Continuum of a Field-Induced Quantum Spin Liquid in $\alpha$-RuCl${}_3$
• Spin-orbit excitations and electronic structure of the putative Kitaev magnet $\alpha$-RuCl${}_3$
• Relation between Kitaev magnetism and structure in $\alpha$-RuCl${}_3$
• Sample dependence of the half-integer quantized thermal Hall effect in the Kitaev candidate $\alpha$-RuCl${}_3$
• Quantization of the thermal Hall conductivity at small Hall angles
• Approximately quantized thermal Hall effect of chiral liquids coupled to phonons
• Antiferromagnetic resonance and terahertz continuum in $\alpha -$RuCl${}_3$
• Anisotropic susceptibilities in the honeycomb Kitaev system $\alpha$-RuCl${}_3$
• Thermodynamic evidence of fractionalized excitations in α-RuCl3
• Field-induced intermediate ordered phase and anisotropic interlayer interactions in $\alpha$-RuCl${}_3$
• Unveiling Magnetic Interactions of Ruthenium Trichloride via Constraining Direction of Orbital moments: Potential Routes to Realize Quantum Spin Liquid
• Electronic and magnetic properties of the monolayer RuCl${}_3$: A first-principles and Monte Carlo study
• Possible Structural Transformation and Enhanced Magnetic Fluctuations in Exfoliated $\alpha$-RuCl${}_3$
• Signatures of low-energy fractionalized excitations in $\alpha$-RuCl${}_3$ from field-dependent microwave absorption
• Deriving models for the Kitaev spin-liquid candidate material $\alpha$-RuCl${}_3$ from first principles
• Scale-invariant magnetic anisotropy in RuCl${}_3$ at high magnetic fields
• Electronic and phonon excitations in α-RuCl${}_3$
• Phonon renormalization in the Kitaev quantum spin liquid
• Polarization-resolved Raman spectroscopy of α-RuCl3 and evidence of room temperature two-dimensional magnetic scattering
• Rare-earth chalcohalides: A family of van der Waals layered Kitaev spin liquid candidates
• THz excitations in α-RuCl3: Majorana fermions, rigid-plane shear and compression modes
• Temperature evolution of the phonon dynamics in the Kitaev spin liquid