27 June 1pm AEST

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Abstract: Conical intersections occur between energy bands in certain two-dimensional periodic lattices. Wavepacket dynamics in the vicinity of a conical intersection mimics that of relativistic spinor particles, where the role of the particle spin is played by an internal spin-like "pseudospin" degree of freedom within the lattice. I will discuss intruiging relations between this pseudospin and other forms of angular momentum, focusing on the pseudospin-1/2 "Dirac cone" between two bands, which occurs in the electronic band structure of graphene. I will then show how Dirac cones can be generalised to pseudospin-1 and pseudospin-2 conical intersections using relatively simple and experimentally-feasible periodic lattice potentials. These findings are applicable to a variety of systems admitting mean field dynamics governed by Schrödinger-type equations, including photonic crystals, Bose-Einstein condensates in optical lattices, and exciton-polariton condensates in structured microcavities.