Cheng Bing, Cheng Di, Lee Kyuho, Luo Liang, Chen Zhuoyu, Lee Yonghun, Wang Bai Yang, Mootz Martin, Perakis Ilias E, Shen Zhi-Xun, Hwang Harold Y, Wang Jigang
Ames National Laboratory, Ames, IA, USA.
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
Nat Mater. 2024 Jun;23(6):775-781. doi: 10.1038/s41563-023-01766-z. Epub 2024 Jan 5.
The discovery of superconductivity in infinite-layer nickelates established another category of unconventional superconductors that shares structural and electronic similarities with cuprates. However, key issues of the superconducting pairing symmetry, gap amplitude and superconducting fluctuations are yet to be addressed. Here we utilize static and ultrafast terahertz spectroscopy to address these. We demonstrate that the equilibrium terahertz conductivity and non-equilibrium terahertz responses of an optimally Sr-doped nickelate film (superconducting transition temperature of T = 17 K) are in line with the electrodynamics of d-wave superconductivity in the dirty limit. The gap-to-T ratio (2Δ/kT) is found to be 3.4, indicating that the superconductivity falls in the weak coupling regime. In addition, we observed substantial superconducting fluctuations near T that do not extend into the deep normal state as the optimally hole-doped cuprates do. Our results support a d-wave system that closely resembles the electron-doped cuprates.
无限层镍酸盐中超导电性的发现确立了另一类非常规超导体，这类超导体与铜酸盐在结构和电子方面具有相似性。然而，超导配对对称性、能隙幅度和超导涨落等关键问题仍有待解决。在此，我们利用静态和超快太赫兹光谱来解决这些问题。我们证明，最佳锶掺杂镍酸盐薄膜（超导转变温度T = 17 K）的平衡太赫兹电导率和非平衡太赫兹响应符合脏极限下d波超导的电动力学。能隙与温度之比（2Δ/kT）为3.4，表明该超导电性处于弱耦合 regime。此外，我们观察到在T附近存在大量超导涨落，但不像最佳空穴掺杂铜酸盐那样延伸到深正常态。我们的结果支持了一个与电子掺杂铜酸盐非常相似的d波系统。
