Nodeless superconducting gap and electron-boson coupling in (La,Pr,Sm)<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub> films.
basic_science · Level V
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- Record sourced from PubMed, PMID 42166557.
- Also identified by DOI 10.1126/science.adw8329.
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Abstract
The discovery of superconductivity in Ruddlesden-Popper bilayer nickelate films under ambient pressure provides an opportunity to directly investigate electronic energy scales of the superconducting state and the pairing mechanism. We report angle-resolved photoemission spectroscopy measurements of superconducting (La,Pr,Sm)<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub> thin films by developing an ultrahigh-vacuum cryogenic sample quenching and transfer technique. A superconducting gap of ~18 milli-electron volts with coherence peaks is observed along the Brillouin zone diagonal. The finite gap persists across the entire Brillouin zone, revealing the absence of gap nodes. A kink is observed in the energy-momentum dispersion at ~70 milli-electron volts below the Fermi level, indicating an electron-boson coupling. The simultaneous observation of a nodeless superconducting gap and electron-boson coupling provides insight into the pairing symmetry and gluing mechanism in Ruddlesden-Popper bilayer nickelates.