QDev Seminar: Elia Strambini

NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore, Pisa, Italy

Topological and non-Topological transitions in hybrid superconducting nanodevices

Nowadays superconductivity is regularly used as fundamental ingredient to engineer exotic states in mesoscopic devices. These states are deeply investigated in hybrid systems aiming to the implementation of novel quantum technologies or the realization of new paradigms of quantum physics. 

In this presentation I’ll review few key experiments in which different exotic phenomena have been observed in superconducting devices. Starting from the topological superconductivity responsible for Majorana bound states and traced (also) in the critical current of Josephson junctions made with strong spin-orbit nanowires¹, I’ll focus the discussion towards unexplored topologies recently introduced in multi-terminal Josephson junctions² and observed in superconducting interferometers³. Then, I will discuss a non-topological transition observed in the resistance of tunnel junctions made with superconducting(Al)/ferromagnetic(EuS) bilayers towards the implementation of the absolute spin-valve effect⁴ and a new concept of superconducting RAM⁵. Finally I’ll comment on the recent discovery of field-effect transition in full-metallic superconducting nanowires⁶.

1.Tiira, J. et al. Magnetically-driven colossal supercurrent enhancement in InAs nanowire Josephson junctions. Nat. Commun. 8, 14984 (2017).

2.Huang, X.-L. & Nazarov, Y. V. Topology protection-unprotection transition: an example from multi-terminal superconducting nanostructures. ArXiv170805549 Cond-Mat (2017).

3.Strambini, E. et al. The ω-SQUIPT as a tool to phase-engineer Josephson topological materials. Nat. Nanotechnol. 11, 1055–1059 (2016).

4.Huertas-Hernando, D., Nazarov, Y. V. & Belzig, W. Absolute Spin-Valve Effect with Superconducting Proximity Structures. Phys. Rev. Lett. 88, 047003 (2002).

5.Patent Application n. 102017000095994 Giazotto, F., Strambini, E., De Simoni, G. & Bergeret Sbabaro, F. S. Superconducting logic element.

6.De Simoni, G., Paolucci, F., Solinas, P., Strambini, E. & Giazotto, F. The Bardeen-Cooper-Schrieffer supercurrent field-effect transistor. ArXiv171002400 Cond-Mat (2017).