Revealing superconducting gap in La3Ni2O7-δ by Andreev reflection spectroscopy under high pressure

Jianning Guo, Yuzhi Chen, Yulong Wang, Hualei Sun, Deyuan Hu, Meng Wang (), Xiaoli Huang () and Tian Cui
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Jianning Guo: Jilin University, State Key Laboratory of High Pressure and Superhard Materials, College of Physics
Yuzhi Chen: Jilin University, State Key Laboratory of High Pressure and Superhard Materials, College of Physics
Yulong Wang: Jilin University, State Key Laboratory of High Pressure and Superhard Materials, College of Physics
Hualei Sun: Sun Yat-sen University, School of Science
Deyuan Hu: Sun Yat-Sen University, Center for Neutron Science and Technology, Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics
Meng Wang: Sun Yat-Sen University, Center for Neutron Science and Technology, Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics
Xiaoli Huang: Jilin University, State Key Laboratory of High Pressure and Superhard Materials, College of Physics
Tian Cui: Jilin University, State Key Laboratory of High Pressure and Superhard Materials, College of Physics

Nature Communications, 2025, vol. 16, issue 1, 1-8

Abstract: Abstract 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 Δs1 = 23 meV and Δs2 = 6 meV, while the BTK fitting consistent with an s-like, two-gap spectrum. The gap ratio 2Δs1(0)/kBTc is found to be 7.41, belonging to a family of strongly coupled superconductors. Our findings provide valuable insights into the superconducting gap structures of the pressure-induced superconducting nickelates.

Date: 2025
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DOI: 10.1038/s41467-025-65865-y

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