Stacking-Order-Dependent Excitonic Properties Reveal Interlayer Interactions in Bulk ReS₂

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Rhenium disulfide (ReS2) is an anisotropic 2D van der Waals material with unique excitonic properties.
• Bulk ReS2 exists in two stacking modes, AA and AB, with poorly understood effects of interlayer coupling on excitons.

Purpose of the Study:

• To investigate the influence of different interlayer coupling in AA and AB-stacked ReS2 on excitonic properties.
• To elucidate the nature of excitons in ReS2 using polarization-dependent optical measurements.

Main Methods:

• Polarization-dependent Raman spectroscopy
• Low-temperature photoluminescence spectroscopy
• Reflection spectroscopy
• Density Functional Theory (DFT) calculations

Main Results:

• Similar in-plane excitonic alignments observed for both AA and AB stacking modes.
• Differences in peak width, position, and anisotropy reveal varying interlayer coupling strengths.
• DFT calculations show similar band structures but altered spin-split states, suggesting different exciton binding energies.

Conclusions:

• Excitonic properties in ReS2 are primarily governed by in-plane interactions but significantly modified by interlayer coupling.
• The pronounced effect of interlayer coupling in ReS2 makes it ideal for studying stacking as a tuning parameter.
• The optical anisotropy of ReS2 positions it as a candidate for polarization-sensitive applications.