Tunable interface states driven by ferroelectric polarization discontinuity in BiFeO₃-based superlattice

Interfacial electronic reconstruction is one of the central topics in condensed matter research as it brings in new physics and novel material properties. Typically, it is induced by dipole, valence, or lattice discontinuities near the interfaces. However, ferroelectric polarization discontinuity (FPD) can also induce electronic reconstruction, which is not well understood, particularly in perovskite oxide interfaces. Here, we demonstrate that FPD plays critical roles in determining the electronic properties of ferroelectric superlattices and creates coexisted two-dimensional hole gas (2DHG) and two-dimensional electron gas (2DEG). We further unravel that FPD competes the traditional polar discontinuity, thus, can lead to various final interface states. The present work opens a special door to achieve 2DEG and 2DHG in the ferroelectric perovskite heterostructure via ferroelectric polarization discontinuity and provides a guidance to achieve emergent interfacial phenomena.