Observation of new fractional quantum Hall states in the first Landau level in graphene

We report on transport studies of the fractional quantum Hall effect in the n=0 and n=1 Landau level of monolayer graphene. The quality of the devices studied here -with mobilities up to 400 000cm2/Vs, and magnetic fields up to 45T- allows us to observe a variety of fractional quantum hall states following the composite fermion sequence, with denominators up to 9. The presence of odd numerator fractions between nu=1 and nu=2 is attributed to the breaking of the valley symmetry and correlates with a zero field insulating state observed at charge neutrality. We discuss the in-plane field dependence of the gaps, which is not trivial and shows dramatic differences between the n=0 and the n=1 Landau levels.