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

Peter Czajka; Tong Gao; Max Hirschberger; Paula Lampen-Kelley; Arnab Banerjee; Nicholas Quirk; David G. Mandrus; Stephen E. Nagler; N. P. Ong

doi:10.1038/s41563-022-01397-w

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

Peter Czajka, Tong Gao, Max Hirschberger, Paula Lampen-Kelley, Arnab Banerjee, Nicholas Quirk, David G. Mandrus, Stephen E. Nagler, N. P. Ong

Research output: Contribution to journal › Article › peer-review

24 Scopus citations

Abstract

The honeycomb magnet α-RuCl₃ has attracted considerable interest because it is proximate to the Kitaev Hamiltonian whose excitations are Majoranas and vortices. The thermal Hall conductivity κ_xy of Majorana fermions is predicted to be half-quantized. Half-quantization of κ_xy/T (T, temperature) was recently reported, but this observation has proven difficult to reproduce. Here, we report detailed measurements of κ_xy on α-RuCl₃ with the magnetic field B ∥ a (zigzag axis). In our experiment, κ_xy/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_xy/T.

Original language	English (US)
Journal	Nature Materials
DOIs	https://doi.org/10.1038/s41563-022-01397-w
State	Accepted/In press - 2022

All Science Journal Classification (ASJC) codes

Chemistry(all)
Materials Science(all)
Condensed Matter Physics
Mechanics of Materials
Mechanical Engineering

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title = "Planar thermal Hall effect of topological bosons in the Kitaev magnet α-RuCl3",

abstract = "The honeycomb magnet α-RuCl3 has attracted considerable interest because it is proximate to the Kitaev Hamiltonian whose excitations are Majoranas and vortices. The thermal Hall conductivity κxy of Majorana fermions is predicted to be half-quantized. Half-quantization of κxy/T (T, temperature) was recently reported, but this observation has proven difficult to reproduce. Here, we report detailed measurements of κxy on α-RuCl3 with the magnetic field B ∥ a (zigzag axis). In our experiment, κxy/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 κxy/T.",

author = "Peter Czajka and Tong Gao and Max Hirschberger and Paula Lampen-Kelley and Arnab Banerjee and Nicholas Quirk and Mandrus, {David G.} and Nagler, {Stephen E.} and Ong, {N. P.}",

note = "Funding Information: We acknowledge useful discussions with I. Sodemann and S. Todadri. P.C., T.G., N.Q. and N.P.O. were supported by the US Department of Energy (DE-SC0017863), by a Materials Research Science and Engineering Centers award from the US National Science Foundation (DMR 2011750) and by the Gordon and Betty Moore Foundation EPiQS initiative through grant GBMF9466 (to N.P.O.). A.B. and S.E.N. were supported by the Quantum Science Center, a National Quantum Information Science Research Center of the US Department of Energy. P.L.-K. and D.G.M. were supported by the Gordon and Betty Moore Foundation{\textquoteright}s EPiQS initiative through grant GBMF9069. Publisher Copyright: {\textcopyright} 2022, The Author(s), under exclusive licence to Springer Nature Limited.",

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doi = "10.1038/s41563-022-01397-w",

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AU - Czajka, Peter

AU - Gao, Tong

AU - Hirschberger, Max

AU - Lampen-Kelley, Paula

AU - Banerjee, Arnab

AU - Quirk, Nicholas

AU - Mandrus, David G.

AU - Nagler, Stephen E.

AU - Ong, N. P.

N1 - Funding Information: We acknowledge useful discussions with I. Sodemann and S. Todadri. P.C., T.G., N.Q. and N.P.O. were supported by the US Department of Energy (DE-SC0017863), by a Materials Research Science and Engineering Centers award from the US National Science Foundation (DMR 2011750) and by the Gordon and Betty Moore Foundation EPiQS initiative through grant GBMF9466 (to N.P.O.). A.B. and S.E.N. were supported by the Quantum Science Center, a National Quantum Information Science Research Center of the US Department of Energy. P.L.-K. and D.G.M. were supported by the Gordon and Betty Moore Foundation’s EPiQS initiative through grant GBMF9069. Publisher Copyright: © 2022, The Author(s), under exclusive licence to Springer Nature Limited.

PY - 2022

Y1 - 2022

N2 - The honeycomb magnet α-RuCl3 has attracted considerable interest because it is proximate to the Kitaev Hamiltonian whose excitations are Majoranas and vortices. The thermal Hall conductivity κxy of Majorana fermions is predicted to be half-quantized. Half-quantization of κxy/T (T, temperature) was recently reported, but this observation has proven difficult to reproduce. Here, we report detailed measurements of κxy on α-RuCl3 with the magnetic field B ∥ a (zigzag axis). In our experiment, κxy/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 κxy/T.

AB - The honeycomb magnet α-RuCl3 has attracted considerable interest because it is proximate to the Kitaev Hamiltonian whose excitations are Majoranas and vortices. The thermal Hall conductivity κxy of Majorana fermions is predicted to be half-quantized. Half-quantization of κxy/T (T, temperature) was recently reported, but this observation has proven difficult to reproduce. Here, we report detailed measurements of κxy on α-RuCl3 with the magnetic field B ∥ a (zigzag axis). In our experiment, κxy/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 κxy/T.

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

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