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Collective spin-wave excitations – magnons – in a quantum Hall ferromagnet are promising quasi- particles for next-generation spintronics devices, including platforms for information transfer. Detec- tion of these charge-neutral excitations relies on the conversion of magnons into electrical signals in the form of excess electrons and holes, but if these signals are equal the magnon detection remains elusive. In this work, we overcome this shortcoming by measuring the electrical noise generated by magnons. We use the symmetry-broken quantum Hall ferromagnet of the zeroth Landau level in graphene to launch magnons. Absorption of these magnons creates excess noise above the Zeeman energy and remains finite even when the average electrical signal is zero. Moreover, we formulate a theoretical model in which the noise is generated by equilibration (partial or full, depending on the bias voltage) between edge channels and propagating magnons. Our model, which agrees with ex- perimental observations, also allows us to pinpoint the regime of ballistic magnon transport in our device.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Spin-wave excitations, quantum Hall ferromagnets, electrical noise

Date published: 2024-06-12

Publisher: Springer Science and Business Media LLC

Journal:

• Nature Communications (ISSN: 20411723) vol. 15 issue. 1 4998

Funding:

• DST | Science and Engineering Research Board SP/SERB-22-0387

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1038/s41467-024-49446-z

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Updated at: 2025-02-07 12:30:30 +0900

Published on MDR: 2025-02-07 12:30:30 +0900