Enhanced spin Seebeck effect signal due to spin-momentum locked topological surface states

TL;DR

This paper demonstrates that topological surface states with spin-momentum locking significantly enhance the spin Seebeck effect in a heterojunction, enabling efficient electrical detection of magnon decay with tunable properties for spintronics applications.

Contribution

It introduces a novel approach to enhance the spin Seebeck effect using topological insulator surface states with spin-momentum locking, showing tunability by Fermi level adjustment.

Findings

Large electromotive force observed when Fermi level is in the bulk gap.

Enhanced spin Seebeck signal compared to metallic systems.

Tunable effect via Fermi level positioning.

Abstract

Spin-momentum locking in protected surface states enables efficient electrical detection of magnon decay at a magnetic-insulator/topological-insulator heterojunction. Here we demonstrate this property using the spin Seebeck effect, i.e. measuring the transverse thermoelectric response to a temperature gradient across a thin film of yttrium iron garnet, an insulating ferrimagnet, and forming a heterojunction with (BixSb1-x)2Te3, a topological insulator. The non-equilibrium magnon population established at the interface can decay in part by interactions of magnons with electrons near the Fermi energy of the topological insulator. When this decay channel is made active by tuning (BixSb1-x)2Te3 to a bulk insulator, a large electromotive force emerges in the direction perpendicular to the in-plane magnetization of yttrium iron garnet. The enhanced, tunable spin Seebeck effect which occurs when the Fermi level lies in the bulk gap offers unique advantages over the usual spin Seebeck effect in metals and therefore opens up exciting possibilities in spintronics.