Stability of germanene under tensile strain

The stability of germanene under biaxial tensile strain and the accompanying modifications of the electronic properties are studied by density functional theory. The phonon spectrum shows that up to $16\%$ strain the germanene lattice is stable, where the Dirac cone shifts towards higher energy and hole-doped Dirac states are achieved. The latter is due to weakening of the Ge-Ge bonds and reduction of the s-p hybridization. Our calculated Gr\"uneisen parameter shows a similar dependence on the strain as reported for silicene (which is different from that of graphene).