电子科技大学乔梁团队报道了氢在镍酸盐中超导的关键作用。相关研究成果于2023年3月1日发表于国际顶尖学术期刊《自然》。

到目前为止，新发现的镍超导体仅存在于通过与金属氢化物的拓扑反应合成的外延薄膜中。该方法通过顶端氧的脱嵌将镍化物从钙钛矿变为无限层结构。这种化学反应可能会引入氢（H），从而影响最终材料的物理特性。不幸的是，H对大多数表征技术不敏感，并且由于其重量轻而难以检测。

该文中，在最佳Sr掺杂的Nd0.8Sr0.2NiO2H外延膜中，二次离子质谱显示以Nd0.8Sr0.21NiO2Hx（x0.2–0.5）的形式存在丰富的H。在0.22≤x≤0.28的非常窄的H掺杂窗口内发现零电阻率，明确显示了H在超导电性中的关键作用。共振非弹性X射线散射证明了起源于顶端氧脱嵌的流动间隙s（IIS）轨道的存在。密度泛函理论计算表明，电负性H–占据了湮灭IIS轨道的顶端氧位点，减少了IIS–Ni 3d轨道杂交。这导致掺H Nd0.8Sr0.2NiO2Hx的电子结构更加趋于二维，这可能与观察到的超导性有关。研究人员认为H是外延无限层镍化物中超导性的重要成分。

附：英文原文

Title: Critical role of hydrogen for superconductivity in nickelates

Author: Ding, Xiang, Tam, Charles C., Sui, Xuelei, Zhao, Yan, Xu, Minghui, Choi, Jaewon, Leng, Huaqian, Zhang, Ji, Wu, Mei, Xiao, Haiyan, Zu, Xiaotao, Garcia-Fernandez, Mirian, Agrestini, Stefano, Wu, Xiaoqiang, Wang, Qingyuan, Gao, Peng, Li, Sean, Huang, Bing, Zhou, Ke-Jin, Qiao, Liang

Issue&Volume: 2023-03-01

Abstract: The newly discovered nickelate superconductors so far only exist in epitaxial thin films synthesized by a topotactic reaction with metal hydrides1. This method changes the nickelates from the perovskite to an infinite-layer structure by deintercalation of apical oxygens1,2,3. Such a chemical reaction may introduce hydrogen (H), influencing the physical properties of the end materials4,5,6,7,8,9. Unfortunately, H is insensitive to most characterization techniques and is difficult to detect because of its light weight. Here, in optimally Sr doped Nd0.8Sr0.2NiO2H epitaxial films, secondary-ion mass spectroscopy shows abundant H existing in the form of Nd0.8Sr0.2NiO2Hx (x0.2–0.5). Zero resistivity is found within a very narrow H-doping window of 0.22≤x≤0.28, showing unequivocally the critical role of H in superconductivity. Resonant inelastic X-ray scattering demonstrates the existence of itinerant interstitial s (IIS) orbitals originating from apical oxygen deintercalation. Density functional theory calculations show that electronegative H– occupies the apical oxygen sites annihilating IIS orbitals, reducing the IIS–Ni 3d orbital hybridization. This leads the electronic structure of H-doped Nd0.8Sr0.2NiO2Hx to be more two-dimensional-like, which might be relevant for the observed superconductivity. We highlight that H is an important ingredient for superconductivity in epitaxial infinite-layer nickelates.

DOI: 10.1038/s41586-022-05657-2

Source: https://www.nature.com/articles/s41586-022-05657-2