Spin wave effects in transport between a ferromagnet and a Weyl semimetal surface

TL;DR

This study demonstrates spin wave excitation effects in transport between a ferromagnet and a Weyl semimetal surface, revealing non-Ohmic behavior linked to magnon emission in topological surface states.

Contribution

It provides experimental evidence of spin wave effects in Weyl semimetal surface states through spin-polarized transport measurements.

Findings

Non-Ohmic differential resistance behavior observed

Current-induced switchings indicative of magnon emission

Magnetic field and temperature dependencies support spin wave interpretation

Abstract

We experimentally investigate spin-polarized transport between a ferromagnetic Ni electrode and a surface of Weyl semimetal, realized in a thick WTe$_2$ single crystal. For highly-transparent Ni-WTe$_2$ planar junctions, we observe non-Ohmic $dV/dI(I)$ behavior with an overall increase of differential resistance $dV/dI$ with current bias, which is accomplished by current-induced switchings. This behavior is inconsistent with trivial interface scattering, but it is well known for spin-polarized transport with magnon emission. Thus, we interpret the experimental results in terms of spin wave excitation in spin textures in the WTe$_2$ topological surface states, which is supported by the obtained magnetic field and temperature $dV/dI(I)$ dependencies.