Tailoring the electronic structure in bilayer molybdenum disulfide via interlayer twist

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Molybdenum disulfide (MoS2) is a prominent two-dimensional material with unique electronic and optical properties.
• Controlling the stacking and interlayer interactions in layered materials is crucial for novel functionalities.

Purpose of the Study:

• To investigate the impact of interlayer twist angle on the optical and electronic properties of molybdenum disulfide bilayers.
• To understand the relationship between interlayer alignment and the resulting material characteristics.

Main Methods:

• Fabrication of molybdenum disulfide bilayers with controlled twist angles by stacking single-crystal monolayers.
• Optical characterization techniques including measurement of optical transition energies and Raman spectroscopy.
• Computational analysis using electronic structure calculations.

Main Results:

• Varying the twist angle significantly tunes the indirect optical transition energy and second-harmonic generation.
• Direct optical transition energies and Raman mode frequencies show weaker dependence on the twist angle.
• Electronic structure calculations reveal that twist-dependent interlayer separation, driven by sulfur atom repulsion, causes shifts in indirect optical transition energies.

Conclusions:

• Interlayer alignment is a critical parameter for precisely tailoring the optoelectronic properties of two-dimensional heterostructures like MoS2 bilayers.
• The study highlights the importance of interlayer twist angle in designing next-generation van der Waals heterostructures.