Strain-induced Enhancement of Tc in Infinite-layer Pr0.8Sr0.2NiO2 Films

The mechanism of unconventional superconductivity in correlated materials remains a great challenge in condensed matter physics. The recent discovery of superconductivity in infinite-layer nickelates, as analog to high-Tc cuprates, has opened a new route to tackle this challenge. By growing 8 nm Pr0.8Sr0.2NiO2 films on the (LaAlO3)0.3(Sr2AlTaO6)0.7 substrate, we successfully raise the transition temperature Tc from 9 K in the widely studied SrTiO3-substrated nickelates into 15 K. By combining x-ray absorption spectroscopy with the first-principles and many-body simulations, we find a positive correlation between Tc and the pre-edge peak intensity, which can be attributed to the hybridization between Ni and O orbitals induced by the strain. Our result suggests that structural engineering can further enhance unconventional superconductivity, and the charge-transfer property plays a crucial role in the pairing strength.

关联电子材料中的非常规超导电性机理，仍是凝聚态物理领域的重大科学挑战。近期作为高温铜基超导体（high-Tc cuprates）类比体系的无限层镍基氧化物（infinite-layer nickelates）中发现超导电性，为攻克这一难题开辟了全新路径。本研究通过在(LaAlO3)0.3(Sr2AlTaO6)0.7衬底上生长8 nm的Pr0.8Sr0.2NiO2薄膜，成功将此前广泛研究的钛酸锶（SrTiO3）衬底基镍基氧化物的超导临界转变温度（Tc）从9 K提升至15 K。结合X射线吸收谱（X-ray absorption spectroscopy）与第一性原理（first-principles）、多体模拟（many-body simulations）手段，我们发现Tc与预边峰强度呈正相关关系，该现象可归因于应变诱导的镍（Ni）与氧（O）轨道杂化作用。本研究结果表明，结构工程可进一步强化非常规超导电性，且电荷转移特性对超导配对强度起到关键作用。