• Corpus ID: 246275755

Pairing symmetry in infinite-layer nickelate superconductor

@inproceedings{Chow2022PairingSI,
  title={Pairing symmetry in infinite-layer nickelate superconductor},
  author={Lin Er Chow and S. Kunniniyil Sudheesh and P. Nandi and Shengwei Zeng and Z. T. Zhang and Xiaoqing Du and Zhi Shiuh Lim and Elbert E. M. Chia and Ariando Ariando},
  year={2022}
}

• L. E. Chow, S. Sudheesh, +6 authors A. Ariando
• Published 25 January 2022
• Physics

The superconducting infinite-layer nickelate family has risen as a promising platform for revealing the mechanism of high-temperature superconductivity. However, its challenging material synthesis has obscured effort in understanding the nature of its ground state and low-lying excitations, which is a prerequisite for identifying the origin of the Cooper pairing in high temperature superconductors. In particular, the superconducting gap symmetry of nickelates has hardly been investigated and remains controversial. Here, we report the pairing symmetry of the infinite-layer nickelate determined by London penetration depth measurements in neodymium-based (Nd,Sr)NiO2 and lanthanide-based (La,Ca)NiO2 thin films of high crystallinity. In contrast to the cuprates, our results are inconsistent with a dominant d_(x^2-y^2 )-wave gap. Instead, neodymium-based infinite-layer nickelate follows predominantly isotropic nodeless pairing, while the lanthanide-counterpart follows anisotropic nodeless or nodal + nodeless gap. In addition, the superfluid density shows a long tail near the superconducting transition temperature, which is consistent with the emergence of two-dimensional to three-dimensional crossover in the superconducting state, where the three-dimensional phase coherence possibly originated from the coupling between NiO2 plane and rare-earth spacer layer or large internal pressure from the epitaxial compressive stress. These observations challenge the existing framework and propel further experimental and theoretical interests on the pairing nature of the infinite-layer nickelate family.