The Quest for High(er) Tc in BaBiO3-Based Heterostructures
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Almost all known superconductors with high Tc have layered structure and are quasi two-dimensional (2D) electronically. Among those that are not, hole-doped BaBiO3 has the highest Tc (and also the highest among all oxides other than cuprates). Coincidentally, Bi is a valence-skipping element and a natural candidate for a negative-U center, with the potential of enhancing superconductivity, as often pointed out by Ted Geballe. With this motivation, we have been trying to synthesize quasi-2D embodiments of BaBiO3. The technique we use is atomic-layer-by-layer molecular beam epitaxy (ALL-MBE), which allows for “digital” synthesis of atomically precise heterostructures and superlattices. We have succeeded in synthesizing some novel, artificial, metastable, layered compounds such as Ba3Bi2LaO9. So far, neither has shown superconductivity, but we will persist in trying.
KeywordsBarium bismuthate Molecular beam epitaxy Atomic-layer engineering Metastable compounds
The research at Brookhaven National Laboratory was supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division. X.H. was supported by the Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant GBMF4410.
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