This paper elucidates a bias-free light-induced orbital and spin current through nonlinear response theory in centrosymmetric broken materials, extending the known bulk photovoltaic effect from charge to spin and orbital degrees of freedom. Using 2D nonmagnetic ferroelectric materials (e.g., GeS), the authors reveal a pure orbital moment current (zero electric charge current) perpendicular to the mirror plane, which converts to a pure spin current via spin-orbit coupling. A four-terminal device is proposed to measure these currents, controllable via ferroelectric phase transition.

Xingchi Mu, Yiming Pan, Jian Zhou