Magnonic Noise and Wiedemann-Franz Law

Abstract

We theoretically establish mutual relations among magnetic momentum, heat, and fluctuations of propagating magnons in a ferromagnetic insulating junction in terms of noise and the bosonic Wiedemann-Franz (WF) law. Using the Schwinger-Keldysh formalism, we calculate all transport coefficients of a noise spectrum for both magnonic spin and heat currents, and establish Onsager relations between the thermomagnetic currents and the zero-frequency noise. Making use of the magnonic WF law and the Seebeck coefficient in the low-temperature limit, we theoretically discover universal relations, i.e. being independent of material parameters, for both the nonequilibrium and equilibrium noise, and show that each noise is described solely in terms of thermal conductance. Finally, we introduce a magnonic spin-analog of the Fano factor, noise-to-current ratio, and demonstrate that the magnonic spin-Fano factor reduces to a universal value in the low-temperature limit and it remains valid even beyond a linear response regime.

4+3 pages, 1 figure

References in corpus (16)

• Direct electronic measurement of the spin Hall effect
• Spin Seebeck insulator
• Probing condensed matter physics with magnetometry based on nitrogen-vacancy centres in diamond
• Microscopic approach to current-driven domain wall dynamics
• Magnonic topological insulators in antiferromagnets
• Magnonic quantum Hall effect and Wiedemann-Franz law
• Temperature dependence of the magnon spin diffusion length and magnon spin conductivity in the magnetic insulator yttrium iron garnet
• Two-electron bunching in transport through a QD induced by Kondo correlations
• Spin current noise of the spin Seebeck effect and spin pumping
• Spin Currents and Magnon Dynamics in Insulating Magnets
• Asymmetric Quantum Shot Noise in Quantum Dots
• Theory of spin Peltier effect
• AC magnetization transport and power absorption in non-itinerant spin chains
• Ballistic magnon heat conduction and possible Poiseuille flow in the helimagnetic insulator Cu${}_2$OSeO${}_3$
• Spin Hall noise
• Noise in tunneling spin current across coupled quantum spin chains

Cited by in corpus (14)

• Microscopic theory of spin transport at the interface between the superconductor and a ferromagnetic insulator
• Microscopic Theory of the Spin Hall Magnetoresistance
• The Discrete Noise of Magnons
• Quantum Oscillations of Gilbert Damping in Ferromagnetic/Graphene Bilayer Systems
• Bosonic superfluid transport in a quantum point contact
• Violation of the magnonic Wiedemann-Franz law in the strong nonlinear regime
• Tunable Spin Seebeck Diode with Magnonic Spin Tunneling Junction
• Asymmetric quantum shot noise in magnon transport
• Fluctuations in Spin Dynamics Excited by Pulsed Light
• Universal $1/3$-suppression of magnonic shot noise in diffusive insulating magnets
• Thermomagnetic Anomalies by Magnonic Criticality in Ultracold Atomic Transport
• Thermomagnetic anomalies in quantum magnon transport caused by tunable junction geometries in cold atomic systems
• Voltage-Controlled Magnonic Spin Tunneling Junction
• Direct and alternating magnon spin currents across a junction interface irradiated by linearly polarized laser