Gigantic enhancement of spin Seebeck effect by phonon drag

TL;DR

This paper demonstrates a significant enhancement of the spin Seebeck effect at low temperatures in a magnetic material, driven by nonequilibrium phonons, combining theoretical insights and experimental validation.

Contribution

It reveals the crucial role of phonons in amplifying the spin Seebeck effect and predicts substrate influence on the observed signals.

Findings

Gigantic enhancement of spin Seebeck effect at low temperatures.

Phonons significantly contribute to the effect via drag of spin excitations.

Substrate conditions impact the magnitude of the spin Seebeck signal.

Abstract

We investigate both theoretically and experimentally a gigantic enhancement of the spin Seebeck effect in a prototypical magnet LaY$_2$Fe$_5$O$_{12}$ at low temperatures. Our theoretical analysis sheds light on the important role of phonons; the spin Seebeck effect is enormously enhanced by nonequilibrium phonons that drag the low-lying spin excitations. We further argue that this scenario gives a clue to understand the observation of the spin Seebeck effect that is unaccompanied by a global spin current, and predict that the substrate condition affects the observed signal.