Affiliation: CNRS – University Paris-Saclay

Talk: August 12th,2019

Research Field: STM – spectroscopy, Quantum effects on superconductivity

Hybrid semiconducting-superconducting systems and superconductivity at the Anderson limit

Hybrid semiconducting-superconducting systems have attracted intense interest because of their potential applications to the fields of superconducting spintronic and topological superconductivity. After a brief overview of hybrid superconducting-semiconducting systems, including some recent works in our group [1,2], I will present a scanning tunneling spectroscopy study of superconducting lead (Pb) nanocrystals grown on the (110) surface of InAs.

The existence of Cooper pairing and the nature of superfluid order in clusters with a small number of Fermions are questions of fundamental interest that have implications for various systems, from atomic nucleus to Helium clusters and superconducting nanocrystals. With its atomic resolution capabilities, STM is an ideal instrument for the study of the electronic spectrum of small size superconducting nanocrystals. Yet, so far, such studies have been hampered by the two antagonistic requirements that the substrate must be conducting and the nanocrystals only weakly coupled to this substrate.Instead of a simple metallic substrate, we found that the 2D electron gas of large Fermi wavelength at the surface of InAs provides an ideal substrate for the growth and study of superconducting lead (Pb) nanocrystals in the regime of quantum confinement.

This discovery allowed to study, for the first time by STM, the superconducting parity effect in nanocrystals as function of their volume and to demonstrate unambiguously the validity of the Anderson criterion, conjectured in 1959, for the existence of superconductivity in nanocrystals submitted to quantum size effects [3].

References:
1. Assouline, A. et al. Spin-Orbit induced phase-shift in Bi2Se3 Josephson junctions.
Nat. Commun. 10, 126 (2019).
2. Assouline, A. et al. Shiba Bound States across the Mobility Edge in Doped InAs Nanowires.
Phys. Rev. Lett. 119, 097701 (2017).
3. Vlaic, S. et al. Superconducting parity effect across the Anderson limit.
Nat. Commun. 8, 14549 (2017).