Interband magnon drag in ferrimagnetic insulators

Abstract

We propose a new drag phenomenon, an interband magnon drag, and report on interaction effects and multiband effects in magnon transport of ferrimagnetic insulators. We study a spin-Seebeck coefficient $S_{\text{m}}$, a magnon conductivity ${\sigma }_{\text{m}}$, and a magnon thermal conductivity ${\kappa }_{\text{m}}$ of interacting magnons for a minimal model of ferrimagnetic insulators using a $1/S$ expansion of the Holstein-Primakoff method, the linear-response theory, and a method of Green's functions. We show that the interband magnon drag enhances ${\sigma }_{\text{m}}$ and reduces ${\kappa }_{\text{m}}$, whereas its total effects on $S_{\text{m}}$ are small. This drag results from the interband momentum transfer induced by the magnon-magnon interactions. We also show that the higher-energy band magnons contribute to $S_{\text{m}}$, ${\sigma }_{\text{m}}$, and ${\kappa }_{\text{m}}$ even for temperatures smaller than the energy difference between the two bands.

14 pages, 4 figures, 1 table; published version

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Cited by in corpus (1)

• Magnon drag induced by magnon-magnon interactions characteristic of noncollinear magnets