Oscillations of the thermal conductivity in the spin-liquid state of α-RuCl3

• Published in: Nature physics 2021-08, Vol.17 (8), p.915-919
• Main Authors: Czajka, Peter, Gao, Tong, Hirschberger, Max, Lampen-Kelley, Paula, Banerjee, Arnab, Yan, Jiaqiang, Mandrus, David G., Nagler, Stephen E., Ong, N. P.
• Format: Article
• Language: English
• Subjects: 639/766/119/2792/4128; 639/766/119/997; Amplitudes; Antiferromagnetism; Atomic; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Entanglement; Field strength; Heat conductivity; Heat transfer; Letter; Low temperature; Magnetic fields; magnetic properties and materials; MATERIALS SCIENCE; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Oscillations; Physics; Physics and Astronomy; Ruthenium trichloride; Spin liquid; Theoretical; Thermal conductivity; topological insulators
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-021-01243-x

In the class of materials called spin liquids 1 – 3 , a magnetically ordered state cannot be attained even at millikelvin temperatures because of conflicting constraints on each spin; for example, from geometric or exchange frustration. The resulting quantum spin-liquid state is currently of intense interest because it exhibits unusual excitations as well as wave-function entanglement. The layered insulator α-RuCl 3 orders as a zigzag antiferromagnet at low temperature in zero magnetic field 4 . The zigzag order is destroyed when a magnetic field is applied parallel to the zigzag axis. At moderate magnetic field strength, there is growing evidence that a quantum spin-liquid state exists. Here we report the observation of oscillations in its thermal conductivity in that field range. The oscillations, whose amplitude is very large within this field range and strongly suppressed on either side, are periodic. This is analogous to quantum oscillations in metals, even though α-RuCl 3 is an excellent insulator with a large gap. As the temperature is raised above 0.5 K, the oscillation amplitude decreases exponentially, anticorrelating with the emergence of an anomalous planar thermal Hall conductivity above approximately 2 K. Transport measurements on the Kitaev quantum spin liquid candidate α-RuCl3 subjected to a magnetic field reveal oscillating behaviour in its thermal conductivity, reminiscent of Shubnikov de Haas oscillations in metals.