Single-particle tunneling spectrum with a robust superconducting gap in La ₂ PrNi ₂ O ₇ thin films at ambient pressure

The recent discovery of high-temperature superconductivity in nickelate systems has generated tremendous interest in the community. The core issue to understand the pairing mechanism is the superconducting gap and its symmetry. We have successfully synthesized the superconducting thin films of La 2 PrNi 2 O 7 with an onset transition temperature of 41.5 kelvins and measured the superconducting tunneling spectra after exposing the superconducting layer by using the tip-excavation technique. The spectrum shows a robust superconducting gap at about Δ ≈ 19 milli–electron volts, and fittings based on the Dynes model indicate that this dominant gap should have an s -wave structure with low anisotropy, which allows us to put the priority in selecting the s ± pairing symmetry. Furthermore, a clear hump structure is observed at an energy of 49 ± 2 milli–electron volts, which is inclined to be interpreted as a bosonic mode. Our results help clarify the mystery of superconductivity in bilayer nickelate superconductors.