Jabir Ali Ouassou

Triplet Cooper pairs induced in diffusive s -wave superconductors interfaced with strongly spin-polarized magnetic insulators or half-metallic ferromagnets

Interfacing superconductors with strongly spin-polarized magnetic materials opens the possibility to discover new spintronic devices in which spin-triplet Cooper pairs play a key role. Motivated by the recent derivation of spin-polarized quasiclassical boundary conditions capable of describing such a scenario in the diffusive limit, we consider the emergent physics in hybrid structures comprised of a conventional s-wave superconductor (e.g. Nb, Al) and either strongly spin-polarized ferromagnetic insulators (e.g. EuO, GdN) or halfmetallic ferromagnets (e.g. CrO2, LCMO). In contrast to most previous works, we focus on how the superconductor itself is influenced by the proximity effect, and how the generated triplet Cooper pairs manifest themselves in the self-consistently computed density of states (DOS) and the superconducting critical temperature Tc. We provide a comprehensive treatment of how the superconductor and its properties are affected by the triplet pairs, demonstrating that our theory can reproduce the recent observation of an unusually large zero-energy peak in a superconductor interfaced with a half-metal, which even exceeds the normal-state DOS. We also discuss the recent observation of a large superconducting spin-valve effect with a Tc change ~1 K in superconductor/half-metal structures, in which case our results indicate that the experiment cannot be explained fully by a long-ranged triplet proximity effect.

Electric control of superconducting transition through a spin-orbit coupled interface

We demonstrate theoretically all-electric control of the superconducting transition temperature using a device comprised of a conventional superconductor, a ferromagnetic insulator, and semiconducting layers with intrinsic spin-orbit coupling. By using analytical calculations and numerical simulations, we show that the transition temperature of such a device can be controlled by electric gating which alters the ratio of Rashba to Dresselhaus spin-orbit coupling. The results offer a new pathway to control superconductivity in spintronic devices.

Spectroscopic evidence of odd frequency superconducting order

Spin filter superconducting S/I/N tunnel junctions (NbN/GdN/TiN) show a robust and pronounced Zero Bias Conductance Peak (ZBCP) at low temperatures, the magnitude of which is several times the normal state conductance of the junction. Such a conductance anomaly is representative of unconventional superconductivity and is interpreted as a direct signature of an odd frequency superconducting order.

Spin-switch Josephson junctions with magnetically tunable sin( δφ/n ) current-phase relation

With a combination of simple analytical arguments and extensive numerical simulations, we theoretically propose a Josephson junction with

Analytically determined topological phase diagram of the proximity-induced gap in diffusive n -terminal Josephson junctions

n+1

Conservation of spin supercurrents in superconductors

superconductors where the current-phase relation can be toggled in situ between a

Controlling supercurrents and their spatial distribution in ferromagnets

\sin(\delta\varphi)

Microwave control of the superconducting proximity effect and minigap in magnetic and normal metals

and

Critical temperature and tunneling spectroscopy of superconductor-ferromagnet hybrids with intrinsic Rashba-Dresselhaus spin-orbit coupling

\sin(\delta\varphi/n)

Voltage control of superconducting exchange interaction and anomalous Josephson effect

shape using an applied magnetic field. Focusing in particular on the case