paper

Observation of fractional Chern insulators in a van der Waals heterostructure

arXiv:1706.06116 · doi:10.1126/science.aan8458

Abstract

Topologically ordered phases are characterized by long-range quantum entanglement and fractional statistics rather than by symmetry breaking. First observed in a fractionally filled continuum Landau level, topological order has since been proposed to arise more generally at fractional filling of topologically non-trivial "Chern" bands. Here, we report the observation of gapped states at fractional filling of Harper-Hofstadter bands arising from the interplay of a magnetic field and a superlattice potential in a bilayer graphene/hexagonal boron nitride heterostructure. We observe new phases at fractional filling of bands with Chern indices and . Some of these, in and bands, are characterized by fractional Hall conductance---they are `fractional Chern insulators' and constitute a new example of topological order beyond Landau levels.

EMS and AAZ contributed equally to this work. We have corrected a factor of two error in the area of the superlattice unit cell and updated the analysis and calculations accordingly

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