Violation of the magnonic Wiedemann-Franz law in the strong nonlinear regime

Abstract

The celebrated Wiedemann-Franz (WF) law which governs the relation between charge and heat transport traces back to the experimental discovery in 1853 by Wiedemann and Franz. Despite the fundamental difference of the quantum-statistical properties between fermions and bosons, the linear-in-$T$ behavior of the WF law at low temperatures has recently been found to be the universal property by the discovery of the WF law for magnon transport. However, the WF law is for the linear response, and whether or not the universal law is valid even in the nonlinear regime of Bose systems remains an open issue. Here we provide a solution to this fundamental challenge. We show that the ratio of the thermal to spin transport coefficient of magnons in topologically trivial insulating magnets exhibits a different behavior from the linear response and the universal law breaks down in the strong nonlinear regime. This finding is within experimental reach with current device and measurement technologies. Our discovery is the key ingredient in magnon-based spintronics, in the evaluation of the figure of merit for thermomagnetic conversion elements of spintronics devices.

5+3 pages

References in corpus (14)

• Hybridizing ferromagnetic magnons and microwave photons in the quantum limit
• Observation of the Magnon Hall Effect
• Scattering theory of nonlinear thermoelectric transport
• 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
• Nonlinear magnon spin Nernst effect in antiferromagnets and strain-tunable pure spin current
• Spin Currents and Magnon Dynamics in Insulating Magnets
• Ballistic magnon heat conduction and possible Poiseuille flow in the helimagnetic insulator Cu${}_2$OSeO${}_3$
• Generalized $f$-Sum Rules and Kohn formulas on Non-linear Conductivities
• Theory of Nonlinear Response for Charge and Spin Currents
• Exact results for nonlinear Drude weights in the spin-1/2 XXZ chain
• Magnonic thermal transport using the quantum Boltzmann equation
• Nonlinear analog spintronics with van der Waals heterostructures

Cited by in corpus (3)

• Breaking down the magnonic Wiedemann-Franz law in the hydrodynamic regime
• Thermomagnetic anomalies in quantum magnon transport caused by tunable junction geometries in cold atomic systems
• Longitudinal magnon transport properties in the easy-axis XXZ Heisenberg ferromagnet on the face-centered cubic lattice