Emergent superconductivity in doped ferroelectric hafnia

Abstract

Superconductivity and ferroelectricity, representing two distinct forms of ordered states, are typically not found together in the same system, making it even more difficult to create a connection between them. Here, supported by first-principles calculations, we propose that Anderson-Blount's ferroelectriclike metal or, more accurately, a polar metal can manifest in electron-doped polar Pca21 HfO2. In this system, polar phonons and consequently the structural asymmetry are not affected by the presence of itinerant electrons. We find that an optical phonon, featuring atomic displacements orthogonal to the ferroelectric polarization direction, is strongly coupled to doped electrons and can acquire a pronounced electron-phonon coupling strength to activate conventional Bardeen-Cooper-Schrieffer superconductivity. The displacements of polar oxygen atoms in Pca21 HfO2 create a link between ferroelectricity and superconductivity, enabling a tunable superconducting temperature ranging from approximately 10 to 30 Kelvin. Owing to hafnia's compatibility with silicon, we suggest that the HfO2-based polar superconductor presents an opportunity to construct high-performing hybrid integrated systems utilizing switchable quantum states.

Source-reported materials — not catalogue approval

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