We are investigating normal and superconducting material properties of graphene, specifically as they appear in graphene-based Josephson junctions at low temperatures. The unique electronic properties of graphene include extraordinary transport phenomena, such as the half-integer quantum Hall effect, Klein tunneling and specular Andreev reflection. Recently our group discovered supercurrents in graphene in the quantum Hall (QH) regime. In this case, the supercurrent can only flow through the chiral QH edge states counter-propagating on opposite sides of the graphene, because the bulk of graphene is gapped by the magnetic field due to Landau quantization. Since each chiral edge state can only carry charge carriers in one direction the electron and hole states near superconducting contacts have to be mixed into a novel type of Andreev bound states – chiral hybrid edge modes – to complete the bound state between the superconducting leads.
Supercurrent in the Quantum Hall regime
Examining how supercurrent is affected by a magentic field, and how it survives in graphene through edge states.
Phonon Bottleneck in Graphene-Based Josephson Junctions at Millikelvin Temperatures
Investigating the nature of the transitions between the normal and superconducting branches in graphene Josephson junctions.
Phase Diffusion in Graphene-Based Josephson Junctions
Characterizing the nature of the electromagnetic environment and dissipation in graphene with contacts made from lead (Pb).