Unveiling the anisotropy of linear and nonlinear charge-spin conversion in Weyl semimetal TaIrTe4

TL;DR

This study demonstrates the simultaneous observation of nonlinear planar Hall effect and spin-orbit torque in TaIrTe4, revealing anisotropic charge-spin conversion properties that depend on crystallographic direction, advancing understanding of Weyl semimetal spintronics.

Contribution

First combined investigation of NPHE and SOT in TaIrTe4, revealing directional anisotropy and providing a method to separate their contributions.

Findings

Significant anisotropy in charge-spin conversion along [100] and [010] directions.

Stronger nonlinear responses and field-like SOT along [100].

Larger damping-like SOT along [010].

Abstract

In Weyl semimetals, the nonlinear planar Hall effect (NPHE) and spin-orbit torque (SOT) are prominent manifestations of nonlinear and linear charge-spin conversion, respectively. However, simultaneous investigations of these phenomena within a single material system are scarce, limiting our understanding of their intrinsic connection and underlying mechanisms. Here, we report the first simultaneous observation of NPHE and SOT in a TaIrTe4/Py heterostructure. By employing harmonic Hall measurements and developing a magnetic field-dependent method, we successfully separated the contributions from NPHE, field-like SOT, and damping-like SOT, enabling accurate characterization of both linear and nonlinear charge-spin conversion properties. Our experiments revealed significant anisotropy along the [100] and [010] crystallographic directions of TaIrTe4, with stronger nonlinear responses and field-like SOT along the [100] direction, and larger damping-like SOT along the [010] direction. The distinct directional dependence of these phenomena provides new insights into the interplay between surface and bulk contributions to charge-spin conversion in Weyl semimetals. These findings enhance our understanding of anisotropic charge-spin conversion mechanisms in Weyl semimetals, which may inform future research and development of spintronic devices based on topological materials.