Fig. 3: Calculated results of ferroelectric bilayer WTe2.
From: Non-synchronous bulk photovoltaic effect in two-dimensional interlayer-sliding ferroelectrics
a Crystal structure. +P and –P states are adopted from ref. 43. Rectangle in a represents the unit cell, and the double-arrows line means the monolayer transformation under \(\widehat M_{xy}\) symmetry. The lower panel in a denotes the top view of bilayer WTe2 with +P state. b Band structures of +P and –P states. c In-plane and e out-of-plane BPVE coefficients. d In-plane BPVE photocurrent and f out-of-plane BPVE polarization of the +P states with the different directions of polarization of light. The length of arrows in d indicates the magnitude of in-plane BPVE response (in arbitrary unit), where \(\sigma _{xy}^x:\sigma _{xx}^y:\sigma _{yy}^y = 1:0.7: - 1.6\). The width and the color of the ribbon in f denote the magnitude and direction of out-of-plane BPVE response, and \(\sigma {\prime}_{xx}^z:\sigma {\prime}_{yy}^z = 1: - 0.6\).
