Strain-Induced Electronic Structure and Bandgap Transition in Bilayer $\text{MoSe}_{2}$ of AB and AA Stacking Order

The transition-metal dichalcogenides (TMDC) materials have received intensive research interest for strain engineering applications. In this work, we report the biaxial strain $(\varepsilon)$ -induced electronic structure of AB and AA stacked 2L $\text{MoSe}_{2}$ using Density functional theory (DFT) calculations. We found that AB stacked 2L $\mathbf{MoSe}_{2}$ remains its intrinsic indirect bandgap transition $(\Gamma-\Sigma_{\min})$ within the strain range from -1.8 % to +0.3%. An indirect to direct bandgap crossover is observed in AA stacked 2L $\text{MoSe}_{2}$ at a practically achievable strain value of -0.1%. The direct bandgap value for AA-stacked $\mathbf{MoSe}_{2}$ makes it a promising candidate for optoelectronic device applications. For the higher strain (-2% $< \varepsilon >$ 0.5%), both AB and AA stacked 2L $\text{MoSe}_{2}$ have similar bandgap tunability and transition.