Observation of a bubble phase of composite fermions*

Non-interacting composite fermions can be used to account for the majority of fractional quantum Hall states. However, the residual interactions between composite fermions can lead to the formations of more exotic states with complex correlations. We recently observed a bubble phase of composite fermions in a GaAs two-dimensional electron gas sample near Landau level filling factor ν = 5/3. This phase with very interesting correlations was identified via a reentrant behavior of the fractional quantum Hall effect in transport measurements. Our finding reveals a new class of strongly correlated topological phases, driven by the clustering and charge ordering of emergent quasiparticles.