ABSTRACT
Nearly four decades ago, the discovery of superconductivity above 30 K in the copper-oxide compound Ba-La-Cu-O in 3d9 electronic structure shattered the previously conceived limit of superconducting transition temperature (Tc) within the conventional Bardeen–Cooper–Schrieffer (BCS) theory. This breakthrough—"high-temperature (high-Tc) superconductivity” in oxide-based compounds—was celebrated by the 1987 Nobel Prize in Physics, and sparked an era of intense research excitement, famously remembered as the ‘Woodstock of Physics’. Since then, a wide variety of d-electron oxide-based layered materials—including Ti-, Bi-, Ru-, Co-, and Ni-based oxides—have been explored in the search for new high-Tc superconductors beyond those of copper-based materials. Culminating from decades of efforts, superconductivity was recently discovered in nickel oxides with a wide variety of d-electron occupancy, including d9-x state with superconducting transition temperature Tc ~ 40 K, and d7+a state with Tc ~ 90 K. These discoveries demonstrate a broad superconducting landscapes with large superconducting gap energy beyond those of copper’s d9 state, and are highly inspirational for the fundamental understanding of unconventional pairing mechanism with large pairing energy scale, as well as the further exploration of strongly-correlated d-electron high- Tc superconducting materials.
BIOGRAPHY
Dr. Stephen Lin Er Chow is currently a Visiting Scholar at Zhejiang University. As a Presidential Graduate Fellow, he is the youngest winner of the Best Graduate Researcher Award in 2022 during his Ph.D. at the National University of Singapore. He received the Highest Distinction (Honours) for both of his B.Sc. and B.Eng. degrees at NUS and was a Physics Olympian. His works include the understanding and design of high-temperature unconventional superconductivity in strongly-correlated d-electron layered oxides, as well as the demonstration of high-entropy material synthesis approach which effectively obtains pure phase layered nickelate. His present research directions focus on the theoretical understanding, experimental investigation, and synthesis of high-temperature superconducting nickel oxide thin films.
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