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arXiv · 1904.01151

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

Kouki Nakata·Yuichi Ohnuma·Mamoru Matsuo
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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.

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Kouki Nakata, Yuichi Ohnuma, Mamoru Matsuo. 2019-04-02. Universal $1/3$-suppression of magnonic shot noise in diffusive insulating magnets. https://doi.org/10.1103/physrevb.100.014406

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