Oscillations of the thermal conductivity observed in the spin-liquid state of $\alpha$-RuCl${}_3$

Abstract

In the class of materials called spin liquids, a magnetically ordered state cannot be attained even at milliKelvin temperatures because of conflicting constraints on each spin (for e.g. from geometric or exchange frustration). The resulting quantum spin-liquid (QSL) state is currently of intense interest because it exhibits novel excitations as well as wave-function entanglement. The layered insulator $\alpha$-RuCl${}_3$ orders as a zigzag antiferromagnet below $\sim$7 K in zero magnetic field. The zigzag order is destroyed when a magnetic field $\mathbf{H}$ is applied parallel to the zigzag axis a. Within the field interval (7.3, 11) Tesla, there is growing evidence that a QSL state exists. Here we report the observation of oscillations in its thermal conductivity below 4 K. The oscillation amplitude is very large within the interval (7.3, 11) T and strongly suppressed on either side. Paradoxically, the oscillations are periodic in 1/\emph{H}, analogous to quantum oscillations in metals, even though $\alpha$-RuCl${}_3$ is an excellent insulator with a gap of 1.9 eV. By tilting $\mathbf{H}$ out of the plane, we find that the oscillation period is determined by the in-plane component $H_a$. As the temperature is raised above 0.5 K, the oscillation amplitude decreases exponentially. The decrease anticorrelates with the emergence above $\sim$2 K of an anomalous planar thermal Hall conductivity measured with $\mathbf{H}\parallel \mathbf{a}$. To exclude extrinsic artifacts, we carried out several tests. The implications of the oscillations are discussed.

arXiv comment8 pages, 3 figures

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Cited by in corpus (8)

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• The planar thermal Hall conductivity in the Kitaev magnet α-RuCl3
• A magnetic continuum observed by terahertz spectroscopy in a quantum spin liquid candidate BaCo${}_2$(AsO${}_4$)${}_2$
• XY magnetism, Kitaev exchange, and long-range frustration in the $J_{\mathrm{eff}}=1/2$ honeycomb cobaltates
• Possible Intermediate Quantum Spin Liquid Phase in $\alpha$-RuCl${}_3$ under High Magnetic Fields up to 100 T
• Field-angle dependence of thermal Hall conductivity in magnetically ordered Kitaev-Heisenberg system
• Luttinger sum rules and spin fractionalization in the SU(N) Kondo Lattice
• Charge-Neutral Electronic Excitations in Quantum Insulators