Electrical noise spectroscopy of magnons in a quantum Hall ferromagnet

• Published in: Nature communications Vol. 15; no. 1; pp. 4998 - 9
• Main Authors: Kumar, Ravi, Srivastav, Saurabh Kumar, Roy, Ujjal, Park, Jinhong, Spånslätt, Christian, Watanabe, K., Taniguchi, T., Gefen, Yuval, Mirlin, Alexander D., Das, Anindya
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.06.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/119/2794; 639/925/918/1052; Data processing; Electrical noise; Electrons; Elementary excitations; Excitation; Ferromagnetism; Graphene; Humanities and Social Sciences; Information processing; Information transfer; Magnons; multidisciplinary; Noise measurement; Noise propagation; Quantum Hall effect; Science; Science (multidisciplinary); Spectroscopy; Spintronics
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-49446-z

Collective spin-wave excitations, magnons, are promising quasi-particles for next-generation spintronics devices, including platforms for information transfer. In a quantum Hall ferromagnets, detection of these charge-neutral excitations relies on the conversion of magnons into electrical signals in the form of excess electrons and holes, but if the excess electron and holes are equal, detecting an electrical signal is challenging. 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 produced by equilibration between edge channels and propagating magnons. Our model also allows us to pinpoint the regime of ballistic magnon transport in our device. Quantum Hall ferromagnets can host magnons, collective spin-wave excitations, which have possible uses in spin-wave based information processing. Detecting these excitations electrically can be challenging. Here, Kumar, Srivastav, Roy, Park and coauthors demonstrate a noise-based approach to detecting magnons.