High pseudospin fermions in a novel two-dimensional structure and its twisted bilayer

We introduce a novel two-dimensional lattice structure that hosts high pseudospin fermions in its low-energy spectrum as a new pathway for exploring flat-band physics through Moiré engineering. In its twisted bilayer arrangement, the Moiré pattern generates multiple isolated flat bands near the Fermi level and features magic angles where the bands are perfectly flat with high spin Chern numbers. The topological nature of the flat bands implies an enhanced geometric contribution to the superfluid weight, which would raise the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature under a BCS-type pairing potential. We show that the number of flat bands and the associated superfluid weight are substantially larger than in twisted bilayer graphene. The question of materials realization of our model system is discussed.