Correlated insulating states at fractional fillings of moiré superlattices

Yang Xu (), Song Liu, Daniel A. Rhodes, Kenji Watanabe, Takashi Taniguchi, James Hone, Veit Elser (), Kin Fai Mak () and Jie Shan ()
Additional contact information
Yang Xu: Cornell University
Song Liu: Columbia University
Daniel A. Rhodes: Columbia University
Kenji Watanabe: National Institute for Materials Science
Takashi Taniguchi: National Institute for Materials Science
James Hone: Columbia University
Veit Elser: Cornell University
Kin Fai Mak: Cornell University
Jie Shan: Cornell University

Nature, 2020, vol. 587, issue 7833, 214-218

Abstract: Abstract Quantum particles on a lattice with competing long-range interactions are ubiquitous in physics; transition metal oxides1,2, layered molecular crystals3 and trapped-ion arrays4 are a few examples. In the strongly interacting regime, these systems often show a rich variety of quantum many-body ground states that challenge theory2. The emergence of transition metal dichalcogenide moiré superlattices provides a highly controllable platform in which to study long-range electronic correlations5–12. Here we report an observation of nearly two dozen correlated insulating states at fractional fillings of tungsten diselenide/tungsten disulfide moiré superlattices. This finding is enabled by a new optical sensing technique that is based on the sensitivity to the dielectric environment of the exciton excited states in a single-layer semiconductor of tungsten diselenide. The cascade of insulating states shows an energy ordering that is nearly symmetric about a filling factor of half a particle per superlattice site. We propose a series of charge-ordered states at commensurate filling fractions that range from generalized Wigner crystals7 to charge density waves. Our study lays the groundwork for using moiré superlattices to simulate a wealth of quantum many-body problems that are described by the two-dimensional extended Hubbard model3,13,14 or spin models with long-range charge–charge and exchange interactions15,16.

Date: 2020
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DOI: 10.1038/s41586-020-2868-6

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