Light‐Induced Giant Enhancement of the Nonlinear Hall Effect in Two‐Dimensional Electron Gases at KTaO ₃ (111) Interfaces

ABSTRACT The nonlinear Hall effect (NLHE), an emergent phenomenon in noncentrosymmetric systems, enables the generation of a transverse voltage without an external magnetic field through a second‐order electrical response. However, achieving a sizable NLHE signal remains a critical challenge for its application in frequency‐doubling and rectifying devices. Here, we report a light‐induced giant enhancement of the NLHE in the 2D electron gas (2DEG) at the CaZrO ₃ /KTaO ₃ (111) interface. Under illumination, the second harmonic Hall voltage increases substantially and undergoes a sign reversal. Correspondingly, the second‐order transverse conductivity ( σ (2) yxx) increases by nearly five orders of magnitude, reaching 2.4 µm V ⁻¹ Ω ⁻¹ , while also reversing its sign. Scaling analysis identifies skew scattering as the dominant mechanism, which is highly tunable via optical gating. Photoexcitation pumps electrons from in‐gap states into the Ta 5 d conduction band, generating high‐mobility photocarriers that increase the cubic scattering time ( τ ³ ) and thereby, dramatically boost σ (2) yxx. First‐principles calculations further reveal that the Berry curvature triple changes sign as the Fermi level approaches the higher‐lying L _z,+ subbands, in the Ta 5 d accounting for the observed sign reversal. Our work offers a new strategy to optically control the NLHE in oxide 2DEG systems, highlighting the tunability of nonlinear transport by optical excitation.