Tunable layer-specific polarizability in twisted multilayer graphene flakes capped with hexagonal boron nitride

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Dielectric properties of low-dimensional materials like twisted multilayer graphene (TMG) capped with hexagonal boron nitride (hBN) are complex.
• The dielectric constant alone is insufficient for characterizing their response to electric fields.
• Accurate measurement and control of field response are challenging.

Purpose of the Study:

• To develop a site-specific polarizability decomposition approach for TMG@hBN.
• To separate and analyze intra- and interlayer polarizabilities.
• To understand the influence of twist angle and hBN encapsulation on dielectric properties.

Main Methods:

• First-principles calculations were employed to develop a site-specific polarizability decomposition method.
• The method was applied to 2580 configurations of TMG flakes with and without hBN encapsulation.
• Layer-resolved analysis of intra- and interlayer contributions was performed.

Main Results:

• Intralayer polarizability dominates the overall dielectric response, while interlayer polarizability dictates variations with twist angle.
• hBN encapsulation enhances interlayer polarizability and reduces its twist-angle dependence.
• Significant interlayer charge transfer response (γ) was observed in outermost graphene layers (γGra) and hBN (γBN), with opposite signs and field-dependent variations.

Conclusions:

• The developed method provides layer-resolved insights into dielectric properties of TMG@hBN.
• Understanding these contributions is key for tuning electric field responses.
• This work offers new strategies for optimizing graphene-based optoelectronic devices.