  Owing to their wide tunability, spin- and valley internal degrees of freedom,
and low disorder, graphene heterostructures are emerging as a promising
experimental platform for fractional quantum Hall (FQH) studies. Surprisingly,
however, transport measurements reveal many fewer FQH states than bulk
capacitive probes. Here, we report the fabrication of dual graphite-gated
monolayer graphene devices in an edgeless Corbino-type geometry that showing
deep FQH sequences. Thermal activation gaps reveal a tunable crossover between
single- and multi-component FQH states in the zero energy Landau level, while
the first Landau level is found to host an unexpected valley-ordered state at
$\nu=-4$.
