Controlled introduction of disorder to probe the superconducting gap symmetry of infinite-layer nickelates : vTools Events

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Controlled introduction of disorder to probe the superconducting gap symmetry of infinite-layer nickelates

#superconductivity #csc #materials #films

Superconductivity in nickelates was first stabilized in thin films of hole doped, infinite-layer (Nd,Sr)NiO2, exhibiting superconducting transition temperatures around 15–20 K under ambient conditions [1]. This marked a significant step forward in the avenue of oxide-based superconductors.

Since then, the field of nickelate superconductivity has rapidly broadened to include a variety of rare-earth and dopant combinations, and also extending to the undoped parent phase. Notably, recent advances in materials synthesis techniques and reduction methods have pushed Tc values even higher, reaching up to 35 K in Sm(Eu,Ca,Sr)NiO2 thin films [2].

While these nickelates share notable similarities with cuprate superconductors - such as layered structures and a 3d9 electron configuration, several key differences have also been observed, particularly in their electronic structures and hybridization behaviour [3]. A fundamental question is the symmetry of the superconducting gap structure in these materials. This remains difficult to probe using techniques commonly used to investigate the paring symmetry in superconductors, such as London penetration depth measurements via mutual inductance [4] or tunnel diode oscillator methods [5], single-particle tunnelling [6], photoemission spectroscopy [7,8], and thermal transport [9], largely due to challenges imposed by thin film geometry and surface degradation caused during the chemical reduction essential to stabilise the requisite Ni valency.

To investigate this, we employ high-energy electron irradiation to systematically introduce pairbreaking defects into infinite-layer nickelate thin films and track resulting changes in superconducting behavior. Our results show a clear suppression of Tc and an increase in normal-state resistivity with increasing disorder which follows an Abrikosov-Gor’kov relation for non-magnetic defects in an unconventional, nodal gap system. These observations provide valuable insights into the superconducting order parameter and electronic landscape of infinite-layer nickelates. More recently, we also explore how these effects depend on choice of rare-earth ion, including Nd-, Pr-, and La-based nickelates.

References

[1] Li, et al. Nature 572, 624 (2019).

[2] Chow, et al. Nature (2025).

[3] Wang, Lee & Goodge. Annu. Rev. Condens. Matter Phys. 15:53, 305 (2024).

[4] Harvey, et al. arXiv:2201.12971v1 (2022).

[5] Chow, et al. arXiv:2201.10038 (2022).

[6] Gu, et al. Nature Communications 11:6027 (2020).

[7] Sun, et al. Science Advances 11, eadr5116 (2025).

[8] Ding, et al. National Science Review 11, nwae194 (2024).

[9] Grissonnanche, et al. Phys. Rev. X 14, 041021 (2024).