https://phys.org/news/2018-09-team-wigner-crystalnot-mott-insulatorin.html

Researchers at the University of Illinois at Urbana-Champaign have recently shown that the insulating behavior reported by the MIT team has been misattributed. Professor Philip Phillips, a noted expert in the physics of Mott insulators, says a careful review of the MIT experimental data by his team revealed that the insulating behavior of the "magic-angle" graphene is not Mott insulation, but something even more profound—a Wigner crystal.

"People have been looking for clear examples of Wigner crystals since Wigner first predicted them in the 1930s," Phillips asserts. "I think this is even more exciting than if it were a Mott insulator."