Engineering Interlayer Hybridization in Energy Space via Dipolar Overlayers

TL;DR

This paper introduces a new approach to engineering interlayer hybridization in van der Waals materials by tuning energy space properties via dipolar overlayers, enabling control over optical, topological, and magnetic features.

Contribution

It proposes a novel method of IH engineering through energy space manipulation using the IH admixture ratio, expanding beyond traditional real-space overlap strategies.

Findings

Tuning ${eta}$ significantly affects interlayer optical transitions.

Adjusting $2{ m riangle}$ switches Dirac surface states.

Controlling magnetic phases in charge density wave systems.

Abstract

The interlayer hybridization (IH) of van der Waals (vdW) materials is thought to be mostly associated with the unignorable interlayer overlaps of wavefunctions ($t$) in real space. Here, we develop a more fundamental understanding of IH by introducing a new physical quantity, the IH admixture ratio ${\alpha}$. Consequently, an exotic strategy of IH engineering in energy space can be proposed, i.e., instead of changing t as commonly used, ${\alpha}$ can be effectively tuned in energy space by changing the onsite energy difference ($2{\Delta}$) between neighboring-layer states. In practice, this is feasible via reshaping the electrostatic potential of the surface by deposing a dipolar overlayer, e.g., crystalline ice. Our first-principles calculations unveil that IH engineering via adjusting $2{\Delta}$ can greatly tune interlayer optical transitions in transition-metal dichalcogenide bilayers, switch different types of Dirac surface states in Bi$_2$Se$_3$ thin films, and control magnetic phase transition of charge density waves in 1H/1T-TaS$_2$ bilayers, opening new opportunities to govern the fundamental optoelectronic, topological, and magnetic properties of vdW systems beyond the traditional interlayer-distance or twisting engineering.