Scanning tunneling microscopy study of robust fractional quantum Hall states in Bernal-stacked bilayer graphene

Fractional quantum Hall states (FQHs) emerge when a 2D electron system is subjected to a strong magnetic field. We performed millikelvin scanning tunneling microscopy (STM) study of the FQHs in Bernal-stacked bilayer graphene. A robust sequence of odd-denominator FQHs are observed, and their charge excitation gaps are characterized. Moreover, we also detected even-denominator FQHs in the lowest Landau levels, highlighting the extra orbital degeneracy for the many-body states. With the imaging power of STM, we can study the spatial variation of these FQH states, and the local excitations when these FQHs experience a defect potential. Our study helps with understanding the charge excitations of these FQHs and opens an opportunity to image anyons.