Anisotropic linear and nonlinear charge-spin conversion in topological semimetal SrIrO3

TL;DR

This paper investigates both linear and nonlinear charge-spin conversion phenomena in the topological semimetal SrIrO3, revealing anisotropic spin textures and their implications for spintronic device functionalities.

Contribution

It provides the first combined study of linear and nonlinear charge-spin conversion in SrIrO3, highlighting anisotropic surface states and their role in spin current generation.

Findings

Nonlinear response depends on crystalline direction.

Anisotropic surface states induce spin-momentum locking.

Spin currents contribute mainly to fieldlike SOT.

Abstract

Over the past decade, utilizing spin currents in the linear response of electric field to manipulate magnetization states via spin-orbit torques (SOTs) is one of the core concepts for realizing a multitude of spintronic devices. Besides the linear regime, recently, nonlinear charge-spin conversion under the square of electric field has been recognized in a wide variety of materials with nontrivial spin textures, opening an emerging field of nonlinear spintronics. Here, we report the investigation of both linear and nonlinear charge-spin conversion in one single topological semimetal SrIrO3(110) thin film that hosts strong spin-orbit coupling and nontrivial spin textures in the momentum space. In the nonlinear regime, the observation of crystalline direction dependent response indicates the presence of anisotropic surface states induced spin-momentum locking near the Fermi level. Such anisotropic spin textures also give rise to spin currents in the linear response regime, which mainly contributes to the fieldlike SOT component. Our work demonstrates the power of combination of linear and nonlinear approaches in understanding and utilizing charge-spin conversion in topological materials.