Field-Induced Interlayer Ion Migration and Electronic Coupling Unlock Ferroelectricity in Centrosymmetric AgInP2Se6 Crystals.

Abstract

The research on two-dimensional (2D) van der Waals (vdW) ferroelectric materials has garnered significant interest due to their novel underlying chemical mechanisms and promising application potential. However, prior studies were largely limited to noncentrosymmetric materials under traditional ferroelectric concepts, hampering the development of vdW ferroelectric systems. Here, we report a centrosymmetric ionic-electronic-coupled vdW ferroelectric semiconductor, AgInP2Se6, where polarization switching arises from electric field-driven interlayer Ag+ migration. Combining density functional theory calculations and in situ second-harmonic generation spectroscopy confirms that at room temperature, the ionic migration barrier prevents spontaneous relaxation, stabilizing the nonvolatile polarization. This discovery expands the landscape of ferroelectric materials beyond symmetry constraints, unlocking new possibilities for low-power, nonvolatile memory and in-memory computing architectures. Using AIPSe as the channel in a ferroelectric semiconductor transistor, we achieve a 69% memory window, an on/off ratio exceeding 106, and exceptional endurance and retention. This study establishes a chemical strategy for modulating polar properties in materials, unveiling unprecedented chemical insights into the ferroelectric regulation of vdW crystals.