Interlayer couplings in homobilayer structures of MSi2X4 (M = Mo/W, X = N/P/As)

TL;DR

This study combines first-principles calculations and analytical models to analyze interlayer couplings in homobilayer MSi2X4 structures, revealing stacking-dependent electrostatic potentials and layer hybridizations relevant for ferroelectricity and topological properties.

Contribution

It provides detailed quantitative analysis of interlayer interactions in MSi2X4 homobilayers, highlighting their stacking dependence and potential for ferroelectric and topological applications.

Findings

Interlayer charge redistribution induces stacking-dependent electrostatic potential up to 0.1 eV.

Interlayer hopping strengths reach tens of meV at valence band maxima.

Layer hybridizations vary significantly with stacking, enabling topological band models.

Abstract

We investigated the interlayer coupling effect in homobilayer structures of MSi2X4 with M = Mo/W and X = N/P/As. Through the combination of first-principles calculations and analytical formulations, the equilibrium interlayer distance, layer energy difference and interlayer hopping strength are obtained for all six MSi2X4 materials, which are found to be insensitive to the type of M atom but differ significantly between X = N and X = P/As. In homobilayers with close to 0{\deg} twist angles, the interlayer charge redistribution introduces a stacking-dependent interlayer electrostatic potential with a magnitude reaching 0.1 eV in MSi2N4, suggesting that it can be an excellent candidate for studying the sliding ferroelectricity. The interlayer hopping strengths are found to be as large as several tens meV at valence band maxima positions K and {\Gamma}, and ~ 1 meV at the conduction band edge K. The resultant layer-hybridizations vary in a large range under different stacking registries, which can be used to simulate honeycomb lattice models with both trivial and non-trivial band topologies.