Polarizable Lattice Induced Persistent and Preferential Electron Self-Trapping in FePSe₃ for Bimodal Operation Artificial Synapse

Artificial synapse (AS) offers a promising approach to emulate biomimetic nervous systems and potentially overcomes the von Neumann bottleneck. Despite their potential, current neuromorphic devices still suffer from challenges, including electrolysis risks, material degradation, ferroelectric fatigue, and irreversible conductance changes from ion migration and trapping. Here, we propose a self-trapping mechanism due to the intrinsic structural distortion of FePSe3 induced by strong electron-phonon (e-ph) coupling, which preferentially captures electrons, forming polarons within 1 picosecond (ps) and extending carrier lifetimes to tens of nanoseconds (ns). A memristor based on polarons formed in FePSe3 via the nondestructive capture and release of electrons transferred from graphene (Gr) was realized, exhibiting a large memory window exceeding 124 V and stable electrical performance over more than 103 switching cycles. Furthermore, FePSe3-Gr devices show good synaptic plasticity stimulated by different amplitudes and numbers of electrical pulses, indicating the capacity to be applied in AS devices. Meanwhile, the synaptic reset function is observed due to the saturation formation of polarons under optical injection. Our findings present a microscopic approach for stable, high-performance AS devices, advancing their application potential in neuromorphic systems.