None-centrosymmetry and topology in ABCBC graphene

Here we investigate ABCBC-stacked pentalayer graphene, a less-studied non-centrosymmetric mixed sequence. Its low-energy band structure contains both a cubic band and a parabolic band that hybridize. In transport measurement, we observe an intrinsic band gap at charge neutrality whose magnitude changes asymmetrically under an applied perpendicular displacement field. Remarkably, two sets of even denominator fractional quantum Hall states appear at high magnetic field, theoretical calculation suggests such states are potential candidates to host non-abelion anyons. Our results establish mixed-stacked multilayer graphene as a tunable platform with various broken symmetries, multiple flatbands and topology, suitable for exploring emergent correlated electronic states.