Capacitance Measurements of Rhombohedral Graphene/hBN Moiré Superlattice: Part II

This talk continues our previous discussion of capacitance measurements of rhombohedral graphene aligned to hexagonal boron nitride. We observe a sequence of fractional Chern insulators at zero magnetic field, along with trivial insulating states at commensurate moiré fillings. By tracking the evolution of the phase diagram as a function of magnetic field, we reveal a unique interplay of topological and trivial phases. Furthermore, capacitance provides a probe of the density of states at the Fermi level, allowing us to extract the thermodynamic charge gap of the most prominent fractional Chern insulators we observe. Having direct access to the density of states, we are able to determine the gap of these phases as a function of displacement field and temperature, characterizing their phase transitions. These gaps are of theoretical interest because they inform how topological phases compete with trivial charge density waves and quarter-metal phases in this topological flat-band regime.