Two-step growth of high-quality single crystals of the Kitaev magnet $\alpha$-RuCl${}_3$

Abstract

The layered honeycomb magnet $\alpha$-RuCl${}_3$ is the most promising candidate for a Kitaev quantum spin liquid (KQSL) that can host charge-neutral Majorana fermions. Recent studies have shown significant sample dependence of thermal transport properties, which are a key probe of Majorana quasiparticles in the KQSL state, highlighting the importance of preparing high-quality single crystals of $\alpha$-RuCl${}_3$. Here, we present a relatively simple and reliable method to grow high-quality single crystals of $\alpha$-RuCl${}_3$. We use a two-step crystal growth method consisting of a purification process by chemical vapor transport (CVT) and a main crystal growth process by sublimation. The obtained crystals exhibit a distinct first-order structural phase transition from the monoclinic ($C2/m$) to the rhombohedral ($R\bar{3}$) structure at $\sim 150$ K, which is confirmed by the nuclear quadrupole resonance spectra with much sharper widths than previously reported. The Raman spectra show the absence of defect-induced modes, supporting the good crystallinity of our samples. The jumps in the thermal expansion coefficient and specific heat at the antiferromagnetic (AFM) transition at 7.6-7.7 K are larger and sharper than those of previous samples grown by the CVT and Bridgman methods and do not show any additional AFM transitions at 10-14 K due to stacking faults. The longitudinal thermal conductivity in the AFM phase is significantly larger than previously reported, indicating a very long mean free path of heat carriers. All the results indicate that our single crystals are of superior quality with good crystallinity and few stacking faults, which provides a suitable platform for studying the Kitaev physics.

9 pages, 7 figures

References in corpus (16)

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• $\alpha$-RuCl3: a Spin-Orbit Assisted Mott Insulator on a Honeycomb Lattice
• Scattering Continuum and Possible Fractionalized Excitations in $\alpha$-RuCl${}_3$
• Successive magnetic phase transitions in $\mathbf{\alpha }$-RuCl${}_3$: XY-like frustrated magnet on the honeycomb lattice
• Anisotropic Ru3+ 4d5 magnetism in the alpha-RuCl3 honeycomb system: susceptibility, specific heat and Zero field NMR
• Robustness of the thermal Hall effect close to half-quantization in a field-induced spin liquid state
• The planar thermal Hall conductivity in the Kitaev magnet α-RuCl3
• Sample dependence of the half-integer quantized thermal Hall effect in the Kitaev candidate $\alpha$-RuCl${}_3$
• Evidence of a Phonon Hall Effect in the Kitaev Spin Liquid Candidate $\alpha$-RuCl${}_3$
• 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${}_3$
• Symmetry-based requirement for the measurement of electrical and thermal Hall conductivity under an in-plane magnetic field
• Stacking disorder and thermal transport properties of $\alpha$-RuCl${}_3$
• Stacking faults in $\alpha$-RuCl${}_3$ revealed by local electric polarization
• Self-selecting vapor growth of transition metal halide single crystals
• Defect-Induced Low-Energy Majorana Excitations in the Kitaev Magnet $\alpha$-RuCl${}_3$

Cited by in corpus (6)

• Kitaev Quantum Spin Liquids
• Superconductivity and a van Hove singularity confined to the surface of a topological semimetal
• Magnetothermal transport in ultraclean single crystals of Kitaev magnet $\alpha$-RuCl${}_3$
• Bulk excitations in ultraclean $\alpha$-RuCl${}_3$: Quantitative evidence for Majorana dispersions in a Kitaev quantum spin liquid
• Intermediate phases in $\alpha$-RuCl${}_3$ under in-plane magnetic field via interlayer spin interactions
• Magnetodielectric Properties in Two Dimensional Magnetic Insulators