Gigantic enhancement of spin Seebeck effect by phonon drag

Adachi, Hiroto; Uchida, Kenichi*; Saito, Eiji; Oe, Junichiro; Takahashi, Saburo; Maekawa, Sadamichi

We investigate both theoretically and experimentally a gigantic enhancement of the spin Seebeck effect in a prototypical magnet LaYFeO 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 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.