Fig. 4: Mechanism on the sliding induced NLO regulation in vdW Cd2GeSe4.
From: Large sliding regulation in van der waals layered nonlinear optical ternary chalcogenides
a Variation of \({\chi }_{123}^{\left(2\right)}\) in the Cd2GeSe4 bilayer systems with different layer distances. All the bilayer systems are formed by stacking two identical monolayers to eliminate the influence of structural difference within each layer on the SHG susceptibility. b Charge density difference between adjacent layers in P-/I-Cd2GeSe4. The areas where the electron density has been enriched/depleted are highlighted in red/blue color. c Charge depletion (blue)/accumulation (red) and the highest occupied orbitals (transparent yellow area) shown together on the Se atoms facing adjacent layers in P-/I-Cd2GeSe4. d Illustration of the three-region model for band composition and SHG contribution in the layered A2MZ4 structures.
