Planar thermal Hall effect of topological bosons in the Kitaev magnet α-RuCl3

The honeycomb magnet α-RuCl 3 has attracted considerable interest because it is proximate to the Kitaev Hamiltonian whose excitations are Majoranas and vortices. The thermal Hall conductivity κ x y of Majorana fermions is predicted to be half-quantized. Half-quantization of κ x y / T ( T , temperatu...

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Bibliographic Details
Published in:Nature materials 2023-01, Vol.22 (1), p.36-41
Main Authors: Czajka, Peter, Gao, Tong, Hirschberger, Max, Lampen-Kelley, Paula, Banerjee, Arnab, Quirk, Nicholas, Mandrus, David G., Nagler, Stephen E., Ong, N. P.
Format: Article
Language:English
Subjects:
639/301/119/997
639/766/119/2792
639/766/483/640
639/925/930
Biomaterials
Bosons
Chemistry and Materials Science
Condensed Matter Physics
Electromagnetism
Excitation
Experiments
Fermions
Hall effect
Laboratories
Letter
Low temperature
Magnetic fields
Magnons
Materials Science
Measurement
Nanotechnology
Optical and Electronic Materials
Phase transitions
Physics
Ruthenium trichloride
Temperature dependence
Temperature profiles
Thermal conductivity
Topology
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Summary:The honeycomb magnet α-RuCl 3 has attracted considerable interest because it is proximate to the Kitaev Hamiltonian whose excitations are Majoranas and vortices. The thermal Hall conductivity κ x y of Majorana fermions is predicted to be half-quantized. Half-quantization of κ x y / T ( T , temperature) was recently reported, but this observation has proven difficult to reproduce. Here, we report detailed measurements of κ x y on α-RuCl 3 with the magnetic field B ∥ a (zigzag axis). In our experiment, κ x y / T is observed to be strongly temperature dependent between 0.5 and 10 K. We show that its temperature profile matches the distinct form expected for topological bosonic modes in a Chern-insulator-like model. Our analysis yields magnon band energies in agreement with spectroscopic experiments. At high B , the spin excitations evolve into magnon-like modes with a Chern number of ~1. The bosonic character is incompatible with half-quantization of κ x y / T . The authors report a strongly temperature-dependent thermal conductivity at low temperature, consistent with topological bosonic modes in a Chern-insulator-like model.
ISSN:1476-1122
1476-4660
DOI:10.1038/s41563-022-01397-w