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

Abstract

Moir\'e 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 Moir\'e patterns on twisted bilayer black phosphorus (tbBP). It is found that the Moir\'e pattern has extraordinary effects and leads to significant asymmetry with respect to transport direction and carrier type. The high-symmetry local stacking configurations in the Moir\'e pattern act as impurities with sizes at the Moir\'e length scale, and these ``Moir\'e 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 $(\ensuremath{\sim}2560\phantom{\rule{0.222222em}{0ex}}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1})$ to just $1.{8}^{\ensuremath{\circ}}$ $(\ensuremath{\sim}131\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1})$. The microscopic physics behind these effects are revealed by the real-space wave functions.