Ballistic multiterminal Josephson effect
We investigate electronic transport in van-der-Waals heterostructures, based in particular on graphene: a carbon-based, two-dimensional material where electrons obey the Dirac equation. Electrons can propagate ballistically over several microns in those heterostructures, so they are an ideal medium to observe quantum phenomena and engineer devices that exploit them.
Mesoscopic superconducting devices are of particular interest to us. We pattern devices where superconducting electrodes are connected by a common graphene island and coupled by the Josephson effect. In those structures, one can observe the propagation of ballistic supercurrents, the multiterminal DC Josephson effect, and the multiterminal inverse AC Josephson effect.
Superconductivity and quantum Hall effect
In graphene, robust quantum Hall states can be observed at a relatively low magnetic field, well below the critical field of certain type-II supercondcutors like Molybdenum Rhenium and Niobium nitride. It is thus possible to engineer devices where superconducting correlations are induced in quantum Hall edge states. Following our observation of the Josephson effect in the quantum Hall regime, we developed devices designed to highlight the microscopic mechanisms allowing superconducting correlations to be induced in edge states and showed how to better control them electrostatically.
Top right: Quantum oscillations of the superconducting current propagating in ballistic graphene. Middle: Magnetic interference pattern in the superconducting current mediated by quantum Hall edge states.
Nonlinear dynamics in Josepshon analog circuits
We develop analog electronic circuits that emulate the dynamical properties of two and three terminal junctions.