Germanene nanomeshes:Cooperative effects of degenerate perturbation and uniaxial strain on tuning bandgap

Based on the detailed first-principles calculations, we have carefully investigated the defect induced band splitting and its combination with Dirac cone move in bandgap opening. The uniaxial strain can split the π -like bands into π_a and π_z bands with energy interval E_strain to shift the Dirac cone. Also, the inversion symmetry preserved antidot can split π_a (π_z) into π_a1 and π_a2 (π_z1 and π_z2) bands with energy interval E_defect to open bandgap in the nanomesh with Γ as four-fold degenerate Dirac point according to the band-folding analysis. Though the E_defect would keep almost unaffected, the E_strain would be increased by enhancing the uniaxial strain to continuously tune the gap width. Then the bandgap can be reversibly switched on/off. Our studies of the inversion symmetry preserved nanomesh show distinct difference in bandgap opening mechanism as compared to the one by breaking the sublattice equivalence in the (GaAs)₆ nanoflake patterned nanomesh. Here, the π-band gap remains almost unchanged against strain enhancing.