Colloquium
Department of Physics, NCU
Proximity-Effect-Induced Superconductivity in Monolayer Ni-Pb Binary Alloy and Ni Nanoislands
Prof. Pin-Jui Hsu (徐斌睿)
Department of Physics, National Tsing Hua University
Center of Quantum Technology, National Tsing Hua University
Date 2022.06.14 (Tue)
Place online
Time 14:00-16:00
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Abstract :
Proximity effect facilitates the penetration of Cooper pairs that permits superconductivity in normal metal with reduced dimensionality, offering a promising approach to develop novel quantum phenomena and emergent phases of matters in hybrid magnetic/superconducting nanostructures. Here, we have investigated proximity-induced superconductivity in monolayer Ni-Pb binary alloy and Ni nanoislands grown on Pb(111) by scanning tunneling microscopy/ spectroscopy (STM/STS) combined with theoretical calculations. Through elemental Pb superconducting substrate, tunneling conductance spectra have resolved an induced anisotropic superconductivity with a gap size Δ about 1.0 meV in the Ni-Pb surface alloy, which is about 0.3 meV smaller than the Pb(111). On the contrary, Ni nanoislands with Kagome lattice display a superconductivity gap with a slightly larger size of the Pb(111) substrate. From spatially monotonic decrease of Δ across the interface between Ni-Pb surface alloy and Pb(111), the short decay length ξL about 3.5 nm has been extracted. According to the Usadel fittings and the BdG model, the momentum dependent electron-phonon interaction offers an explanation for the proximity-induced anisotropic superconductivity in the Ni-Pb surface alloy. As for Kagome-structured Ni nanoislands, asymmetric edge scattering of surface electrons on Pb(111) has been revealed and further theoretical insights on the details of strong suppression of backscattering at the saw-tooth type of edges as well as enhanced superconducting gap are currently in progress.