2025/09/16 by Jianning Guo, Yuzhi Chen, Guo, Jianning +13
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Atomic and Subatomic Physics Research #Classical Physics (physics.class-ph) #FOS: Physical sciences #High-pressure geophysics and materials #Spectroscopy and Laser Applications #Superconductivity (cond-mat.supr-con)
paper · pdf · doi:10.48550/arxiv.2509.12601
openalex publication_date 2025/09/16 · openalex created_date 2025/10/18 · openalex updated_date 2026/07/28
The recent discovery of compressed superconductivity at 80~K in La3Ni2O7-δ has brought nickelates into the family of unconventional high-temperature superconductors. However, due to the challenges of directly probing the superconducting pairing mechanism under high pressure, the pairing symmetry and gap structures of nickelate superconductors remain under intense debate. In this work, we successfully determine the microscopic information on the superconducting gap structure of La3Ni2O7-δ samples subjected to pressures exceeding 20~GPa, by constructing different conductance junctions within diamond anvil cells. By analyzing the temperature-dependent differential conductance spectra within the Blonder--Tinkham--Klapwijk (BTK) model, we have determined the superconducting energy gap at high pressure. The differential conductance curves reveal a two-gap structure with Δ1 = 23~meV and Δ2 = 6~meV, while the BTK fitting is consistent with an s-like, two-gap spectrum. The gap ratio 2Δs1(0) / kBTc is found to be 7.61, belonging to a family of strongly coupled superconductors. Our findings provide valuable insights into the superconducting gap structures of the pressure-induced superconducting nickelates.