Agenda

Résumé : The progress in nanofabrication technology now allows fabricating all kinds of Josephson weak links connecting an arbitrary number of terminals. With my collaborators, as soon as 2011, I generalized to three terminals the Anderson and Josephson works which establish a connection between gauge invariance, the superconducting phase variables and the supercurrent [1]. The resulting microscopic process of the quartets involves a transient intermediate state supporting correlation among four fermions and coupling to the three-body quartet phase. This produces DC-resonance lines when the differential conductance is plotted as a function of the two independent bias voltages, which was observed in the three successive collaborations that were developed with the Lefloch’s group (Grenoble) in metallic devices [2], with the Heiblum’s group (Weizmann Institute) in semi- conducting nanowires [3] and with the Kim’s group (Harvard) in graphene [4].
In this talk, I will introduce the quartets and propose a general theoretical picture [5] for the voltage-biased ballistic 2D metal-based devices, that captures both features of the Kayyalha’s group experiment (Penn State) on three-terminal Andreev interferometers [6] and the Kim’s group experiment (Harvard) on four-terminal Josephson junctions [4]. This new approach is based on both physical ingredients of the spectrum and the electronic populations, starting from the long-junction limit. Their coupling to the two- or three-body Josephson or quartet modes is operated via a new nonlocal Keldysh process that we call as « phase-Andreev reflection » [6,7]. This extends the physics of Andreev interferometers to the ballistic limit and to the multiterminal Josephson effect.