Cascade of even-denominator fractional quantum Hall states in mixed-stacked multilayer graphene.

Abstract

The fractional quantum Hall effect at half-filled Landau levels provides a promising route to unusual topological phases that may host non-Abelian excitations, but these states are often fragile and difficult to control experimentally. Here, we report the observation of a cascade of even-denominator fractional quantum Hall states at fillings ν = -5/2, -7/2, -9/2, -11/2 and -13/2, alongside numerous odd-denominator states in mixed-stacked pentalayer graphene-a system characterized by intertwined quadratic and cubic band dispersions. These even-denominator states emerge from two distinct intra-zeroth Landau levels and exhibit displacement-field tunability. At half fillings, continuous quantum phase transitions between even-denominator states, magnetic Bloch states, and composite Fermi liquids are clearly identified upon tuning external fields. Numerical calculations support possible Moore-Read type pairing for even-denominator states, although direct probes of their exchange statistics remain important for future experiments. These results establish mixed-stacked graphene as a versatile platform for tunable correlated topological phases.