Physics (Internal)

Pseudospin superconductivity in honeycomb superlattices

This event is part of the Graduate Student Council Events.

Part of the student seminar series. A recording will be posted on the event page.

Abstract: Semiconductor artificial graphene (AG) seeks to replicate the properties of graphene, by subjecting a two-dimensional electron gas to a periodic potential with the same symmetries as the atomic lattice in graphene. I will explain how this material can realize a new mechanism for high temperature superconductivity — due to the antiscreened fluctuations of the emergent pseudospin degree of freedom. The Berry phase of the Dirac fermion causes destructive interference between states with opposite momenta, leading to the novel effect whereby electrons can partially avoid the Coulomb repulsion by forming Cooper pairs. This gives rise to an effective attraction between Cooper pairs, which is enhanced by doping due to an antiscreening effect, eventually leading to superconductivity. This mechanism originates solely from the repulsive Coulomb interaction, and relies on a strong periodic potential and the topological properties of the Dirac dispersion — and could therefore in principle be realized in other Dirac materials. The ability to artificially tune the lattice spacing, potential strength and density in AG allows this regime to be engineered, and the calculations I present show that Tc can be order 25 K for realistic experimental parameters.