Broken SU(4) Symmetry and The Fractional Quantum Hall Effect in Graphene

ORAL

Abstract

We describe a simple variational approach to understand the spin-valley broken symmetry states in the fractional quantum Hall regime of graphene. Our approach allows to predict the incompressible ground states and their charge gaps and is able to explain the observed differences between filling factor ranges $|\nu|<1$ and $1<|\nu|<2$. We find that in the SU(4) invariant case the incompressible ground state at $|\nu|=1/3$ is a three-component incompressible state, not the Laughlin state, and discuss the competition between these two states in the presence of SU(4) spin-valley symmetry breaking terms. We find that the lowest energy fractionally charged quasi-particles involve spin/valley flips in several prominent fractions. We discuss the expected behavior of the gaps under tilting the magnetic field away from normal which allows to tune the relative strength of Zeeman and valley symmetry breaking interactions.

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Authors

  • Inti Sodemann

    University of Texas at Austin

  • Allan MacDonald

    The University of Texas at Austin, Department of Physics, University of Texas at Austin, Austin, Texas 78712-1081, USA, Department of Physics, The University of Texas at Austin, Austin, TX, 78712, Department of Physics, University of Texas at Austin, University of Texas at Austin, University of Texas at Austin, Austin, Texas 78712, USA, UT Austin, Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA