Interlayer coupling in commensurate and incommensurate bilayer structures of transition metal dichalcogenides

TL;DR

This paper investigates the interlayer coupling mechanisms in bilayer transition metal dichalcogenides, revealing how phase factors and interference affect coupling strength and implications for ultrafast charge transfer.

Contribution

It provides a perturbative analysis of interlayer couplings in commensurate and incommensurate bilayers, quantifying hopping terms and their effects on charge transfer.

Findings

Interlayer coupling in extpm K valleys decomposed into phase-dependent hopping terms.

Coupling strength in commensurate bilayers varies with translation due to interference.

Strong coupling in extGamma and Q valleys mediates ultrafast charge transfer.

Abstract

The interlayer couplings in commensurate and incommensurate bilayer structures of transition metal dichalcogenides are investigated with perturbative treatment. The interlayer coupling in \pm K valleys can be decomposed into a series of hopping terms with distinct phase factors. In H-type and R-type commensurate bilayers, the interference between the three main terms leads to a sensitive dependence of the interlayer coupling strength on the translation. The magnitudes of the main hopping terms are found to some dozen of meV by fitting to the ab initio results. The interlayer couplings in \Gamma valley of valence band and Q valley of conduction band are also studied. The obtained strong coupling strengths of several hundred meV can play important roles in mediating the ultrafast interlayer charge transfer in heterobilayers of transition metal dichalcogenides.