Signatures of Polar Metal Phase in the Quasi-2D Electron System in PLD-Grown Amorphous-Epitaxial Oxide Heterostructures

For years, itinerant charge carriers in ferroelectric insulators were believed to completely quench ferroelectricity. Recent breakthroughs, however, demonstrated the existence of a novel class of quasi-two-dimensional polar metals with promising applications in nonvolatile electronics and spintronics. Here, by combining temperature-dependent magnetotransport measurements, optical second harmonic generation (SHG), resonant photoemission spectroscopy (ResPES), and X-ray absorption spectroscopy (XAS), we report on the properties of a BaTiO3-based oxide heterostructure, sustaining a persistent polar displacement in the BaTiO3layer while supporting a two-dimensional electron gas. This suggests that the oxide heterostructure may operate as a polar metal system, paving the way for new developments in oxide-based electronics.