Anomalous Dielectric Response at Oxide Heterointerfaces

Two-dimensional charge carrier accumulation at oxide heterointerfaces presents a paradigm shift for oxide electronics. Like a capacitor, interfacial charge buildup couples to an electric field across the dielectric. To prevent the so-called polar catastrophe, several charge screening mechanisms emerge, including polar distortions and interfacial intermixing which reduce the sharpness of the interface. Here, I discuss our efforts to understand how atomic intermixing at oxide interfaces affects the balance between polar distortions and electric potentials across the dielectric. Using first principles calculations, we find that intermixing moves the peak charge distribution away from the interface; thereby changing the direction of polar distortions away from this boundary with minimal effect on the electric field. This opposing electric field and polar distortions is equivalent to the transient phase transition tipping point observed in double well ferroelectrics; resulting in anomalous dielectric responses; a possible signature of local negative differential capacitance with implications for designing dissipationless oxide electronics.