Evidence for the first-order topological phase transition in a Kitaev spin liquid candidate $\alpha$-RuCl${}_3$

Abstract

The Kitaev quantum spin liquid (QSL) on the two-dimensional honeycomb lattice epitomizes an entangled topological state, where the spins fractionalize into Majorana fermions. This state has aroused tremendous interest because it harbors non-Abelian anyon excitations. The half-integer quantized thermal Hall (HIQTH) conductance observed in $\alpha$-RuCl${}_3$ is a key signature of these excitations. However, the fate of this topologically nontrivial state at intense fields remains largely elusive. Here, we report the thermal conductivity $\kappa$ and specific heat $C$ of $\alpha$-RuCl${}_3$ with in-plane magnetic fields $H$. For the field direction perpendicular to the Ru-Ru bond, where the HIQTH effect is observed, we find a discontinuous jump in $\kappa (H)$ and a peak anomaly in $C(H)$ at ${\mu }_0{H}^{\ast }\approx 11$\,T, evidencing a weak first-order phase transition. Remarkably, the HIQTH effect vanishes close to $H^{\ast }$. Furthermore, we find that the spin-fractionalization feature is retained well above $H^{\ast }$. These imply the emergence of the phase transition that separates two QSL phases with distinct topological properties.

6 pages, 4 figures

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• Angle-dependent thermodynamics of $\alpha$-RuCl${}_3$
• Origin of oscillatory structures in the magnetothermal conductivity of the putative Kitaev magnet $\alpha$-RuCl${}_3$
• Stacking faults in $\alpha$-RuCl${}_3$ revealed by local electric polarization
• Topological Nematic Phase Transition in Kitaev Magnets Under Applied Magnetic Fields

Cited by in corpus (15)

• Oscillations in the magnetothermal conductivity of $\mathbf{\alpha }$-RuCl${}_3$: Evidence of transition anomalies
• Symmetry-based requirement for the measurement of electrical and thermal Hall conductivity under an in-plane magnetic field
• Kitaev Quantum Spin Liquids
• Unconventional Magnetic Oscillations in Kagome Mott Insulators
• The sample-dependent and sample-independent thermal transport properties of $\alpha$-RuCl${}_3$
• Nature of visons in the perturbed ferromagnetic and antiferromagnetic Kitaev honeycomb models
• Defect-Induced Low-Energy Majorana Excitations in the Kitaev Magnet $\alpha$-RuCl${}_3$
• Magnetothermal transport in ultraclean single crystals of Kitaev magnet $\alpha$-RuCl${}_3$
• Molecular Orbital Electronic Instability in the van der Waals Kagome Semiconductor Nb${}_3$Cl${}_8$: Exploring Future Directions
• Successive topological phase transitions in two distinct spin-flop phases on the honeycomb lattice
• The Detection of Unconventional Quantum Oscillations in Insulating 2D Materials
• Quantum Spin Liquid phases in Kitaev Materials
• Intermediate phases in $\alpha$-RuCl${}_3$ under in-plane magnetic field via interlayer spin interactions
• Spin-phonon coupling and thermal Hall effect in the Kitaev model
• Jordan-Wigner composite-fermion liquids in 2D quantum spin-ice