Quantum Oscillations across Hole Crystallization in Rhombohedral Graphene

Recent quantum-oscillation measurements in rhombohedral graphene reveal an abrupt increase in the dominant frequency and the emergence of additional frequencies as the carrier density is lowered toward superconductivity. Noninteracting band models can account for multiple frequencies but do not explain the upward jump. We show that these features can arise from two competing fates of the inner hole pocket in an annular Fermi sea: collapse into a simply connected Fermi liquid or crystallization into an anticrystal, in which localized holes coexist with itinerant electrons. Pocket collapse contracts the outer Fermi contour at fixed density, whereas hole crystallization preserves a larger contour that supports magnetic-breakdown orbits. This contrast provides a possible explanation for the frequency jump, while additional reconstructed orbits produce a multitone spectrum. Our results support the anticrystal as a candidate normal state near superconductivity in rhombohedral graphene.