Flexoelectricity and electronic properties of monolayer GaSe under shear strain gradient

Abstract

The flexoelectric effect is a linear coupling phenomenon between electric polarization and mechanical strain gradient. Due to the size dependence, the influence of flexoelectricity on the physical properties of two-dimensional (2D) materials will be very significant. In this paper, we found that inhomogeneous deformation can lead to significant flexoelectric effects in monolayer GaSe. The strain gradient introduced by the deformation along the film thickness leads to out-of-plane ferroelectric polarization and shows an obvious size effect. The shear flexoelectric coefficient of monolayer GaSe is 0.048e, which is one order of magnitude larger than TMDs monolayers. In addition, the strain gradient can modulate the band gap of 2D materials in a wide range, indicating that out-of-plane deformation can dramatically regulate the electronic conductivity and optical properties of GaSe monolayer. Our work reveals that the flexoelectric effect of monolayer GaSe has great application potential in nano-strain engineering and flexible electronics.