Gate‐Tunable Circular Photogalvanic Effects in Two‐dimensional Perovskite Ferroelectric‐based Transistor toward Multi‐state Memory

Spintronics has long been an exciting branch of condensed matter science, among which the spin splitting of energy bands in an inversion asymmetric material endows the circular photogalvanic effects (CPGE) toward high-performance spin-based optoelectronic devices. Here, we have successfully achieved gate-tunable CPGE in a biaxial perovskite ferroelectric (n-HA)₂CsPb₂Br₇ (1, n-HA is n-heptanamine), involving the broken symmetry from its spontaneous polarization. Strikingly, under left- and right-circularly polarized light, this CPGE acquires a large anisotropy factor for photocurrents up to ~1.04, far beyond most organic semiconductors and chiral counterparts (<0.2). It is the large splitting coefficient along the k_y direction (~1.476 eV Å) that contributes to the significant realization of CPGE in 1. Notably, this spin-based CPGE of 1 has been modulated via the gate-voltage manipulation in its transistor-type devices, leading to multi-state memory behaviors. That is, six distinct conductance states are obtained under circularly polarized light, containing the original, high/low-state responses L(-1,0,1) to the left circularly polarized light, as well as three right components R(-1,0,1). This study establishes a pathway for further exploration toward multi-state memory in the field of ferroelectric integrated devices.