▎ 摘　　要

Through magnetotransport measurements, we investigate ultrasmooth graphene bilayer nanoribbons obtained by multiwall carbon nanotube unzipping, under a high magnetic field up to 55 T. The high quality of the samples allows us to observe a Hall quantization in ribbons as narrow as 20 nm. The presence, for certain samples, of isolated peaks in the resistance plateau is found to be related to a very moderate long-range disorder, which induces magnetic-field-dependent interedge scattering. Tight-binding numerical simulations of electron transport illustrate and confirm this picture. Our study provides important insights into the quantum Hall effect in quasi-1D systems and indicates possible lines for future investigations of the nonchiral edge states induced by zigzag nanoribbon sections.