Universal $1/3$-suppression of magnonic shot noise in diffusive insulating magnets

Abstract

Extending a Boltzmann-Langevin theory to magnons, we show a universality of current-noise suppression in diffusive systems against the difference of quantum-statistical properties of bosons and fermions. To this end, starting from a quantum kinetic equation for magnons subjected to thermal gradient in dilute impurities, we derive a bosonic counterpart of the semiclassical Boltzmann-Langevin equation for electrons and evaluate a magnonic current-noise in the diffusive insulating magnet. We theoretically discover that compared with a Poissonian shot noise of magnons in an insulating ferromagnetic junction, the magnonic shot noise is suppressed in the diffusive insulating bulk magnet and noise-to-current ratio (Fano factor) at low temperatures exhibits a universal behavior, i.e., the same suppression $1/3$ as the one for electron transport in diffusive conductors, despite the difference of quantum-statistical properties. Finally, we show that our predictions are within experimental reach with current device and measurement technologies.

4+4 pages; the title has been changed following the suggestion from the publisher

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• Hybridizing ferromagnetic magnons and microwave photons in the quantum limit
• Microscopic approach to current-driven domain wall dynamics
• Spin current noise of the spin Seebeck effect and spin pumping
• Spin Currents and Magnon Dynamics in Insulating Magnets
• Bunching and anti-bunching in electronic transport
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Cited by in corpus (1)

• Magnonic thermal transport using the quantum Boltzmann equation