Fig. 9: Brillouin zone and band structure of the 2.2° twisted bilayer.
From: Covalent bonded bilayers from germanene and stanene with topological giant capacitance effects
a The hexagonal BZ for the 2.2° twisted GeSn bilayer; the points K1, K2, K3 and points M1, M2 and M3 correspond to the unit cell consisting of 182 atoms. Without lattice distortions all K and M points have degenerate bandgaps. The degeneracy is broken when lattice distortions break lattice symmetry to minimize the total energy. b Electronic band structure of the 2.2° twisted GeSn bilayer, where the centre of inversion is absent, demonstrating flat bands and an indirect bandgap of 10 meV.
