Moire impurities in twisted bilayer black phosphorus: Effects on the carrier mobility

Moire patterns on two-dimensional van der Waals heterostructure can give rise to unique electronic and transport properties. In this work we report a theoretical investigation of Moire patterns on twisted bilayer black phosphorus (tbBP). It is found that the Moire pattern has extraordinary effects and leads to significant asymmetry with respect to transport direction and carrier type. The high-symmetry local stacking configurations in theMoir pattern act as impurities with sizes at the Moire length scale, and these Moire impurities induce flatbands and localized states in tbBPs. Because both the conduction band minimum and valence band maximum are dominated by these localized states, the deformation potential limited carrier mobility is significantly affected: the electron mobility of tbBPs reduces by almost 20-fold when twisting from zero angle (similar to 2560 cm(2) V-1 s(-1)) to just 1.8 degrees (similar to 131 cm(2) V-1 s(-1)). The microscopic physics behind these effects are revealed by the real-space wave functions.