  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.
