Broken SU(4) Symmetry and The Fractional Quantum Hall Effect in Graphene
Since its discovery more than three decades ago, the fractional quantum Hall effect has been studied almost exclusively in the two-dimensional electron systems formed in GaAs/AlGaAs heterojunctions. However, recent improvements in the quality of graphene have revealed a rich landscape of fractional quantum Hall states in this material, heralding the beginning of a new chapter in fractional quantum Hall physics.
The N=0 Landau level of graphene is endowed with an approximate spin-valley SU(4) symmetry. In this talk, I will describe a variational approach to understand how this symmetry is broken, which allows to construct trial incompressible ground states, their charged quasi-particles and compute their associated gaps.