Image charge effect in layered materials: Implications for the interlayer coupling in MoS2

The electronic and optical properties of layered materials, such as transition metal dichalcogenides, can be strongly affected by their dielectric environment-this phenomenon is also known as the image charge effect. In multilayers, the stacked crystal structure implies a layer-dependent variation of the image charge effect. However, this variation and its implications on the interlayer coupling are heretofore not well understood. Here, we show that the variation of dielectric screening effects in layered materials can be described by a macroscopic dielectric continuum model within classical electrostatics. We present an efficient method that incorporates this effect in electronic structure calculations. The present method is based on semi-empirical tight-binding and amenable to use for large-scale systems. By applying this method to multilayer MoS2, we find an energetic decoupling of the surface layer-at the K point of the Brillouin zone-which leads to the formation of a surface-layer band gap. More generally, our calculations reveal that the image charge effect can cause spatial modulation of the interlayer coupling by changing the band alignment between the layers.