Amazing stuff!
Magic-angle graphene reveals a host of new states – Physics World: When he subsequently changed the charge carrier density within a device made from the material by applying a varying voltage to it, he observed that the device could be tuned from behaving as a Chern insulator (a state where the material’s electron bands are all either filled or all empty, and for which the filled bands have a net total Berry curvature or Chern number) to a superconductor. It could also be made to form an exotic magnetic state in which magnetism arises because of orbital motion of the electron rather than (as in typical ferromagnets) the electron spin. Such a state, Lu says, has never been seen before. ... that magic-angle bilayer graphene seems to be competing between many novel states. “By tuning the carrier density within the lowest two flat moiré bands, it alternately shows correlated states and superconductivity, together with exotic magnetism and band topology ... the device enters a superconducting state at the lowest carrier densities ever reported for any superconductor ... They were also able to increase the superconducting transition temperature of the material to above 3 K, a value twice that previously reported for magic-angle graphene devices.
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