Enhanced circular photogalvanic effect in oxide two-dimensional electron gas via photoelectric synergistic modulation

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We report a giant enhancement of circular photogalvanic effect (CPGE) in the oxide two-dimensional electron gas at LaAlO 3 / SrTiO 3 and LaAl O 3 / KTa O 3 interfaces through the synergistic ultraviolet (UV) photoexcitation and electrostatic gating. The UV illumination generates high-density photocarriers by promoting valence-to-conduction band transitions, which simultaneously increase the Fermi wave vector k F and Fermi energy E F . Concurrently, the gate-induced oxygen vacancy migration toward the interface amplifies the Rashba spin-orbit coupling coefficient α R . Strikingly, the CPGE photocurrent exhibits a nonmonotonic dependence on both gate voltage and UV intensity, peaking at an optimal carrier density where k F and α R cooperatively enhance the spin-momentum locking. This dual control strategy achieves a CPGE responsivity of 22.71 µV for LaAl O 3 / KTa O 3 interfaces. Our findings establish the photoelectric coupling as a powerful knob for tailoring nonequilibrium spin phenomena in quantum oxide interfaces, with direct implications for reconfigurable spintronic devices.

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