Self-Trapped Interlayer Excitons in van der Waals Heterostructures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Self-trapped states (STS) of interlayer excitons (IXs) significantly influence van der Waals heterostructure (vdWH) properties.
• The microscopic mechanisms driving STS in vdWHs remain a subject of ongoing research and debate.

Purpose of the Study:

• To investigate the influence of exciton-interface optical phonon coupling on IX binding energies in vdWHs.
• To elucidate the mechanisms behind the self-trapped state of IXs and their classification.
• To provide a theoretical explanation for experimental observations of IX spectral shifts.

Main Methods:

• Theoretical study of binding energy corrections due to exciton-phonon coupling.
• Analysis of electron and hole effective mass ratios in four types of vdWHs.
• Classification of self-trapped IX states based on binding energy changes.

Main Results:

• IXs in vdWHs can enter STS when the electron and hole effective mass ratio is appropriate.
• Two types of self-trapped IXs are identified: one with increasing binding energy (tens of meV), consistent with spectral red-shifts, and another with decreasing binding energy, explaining blue-shifts and broadening.
• Interconversion between these two self-trapped states is possible by tuning vdWH structural parameters.

Conclusions:

• The findings offer a deeper understanding of the self-trapped mechanism in IXs within vdWHs.
• This work provides insights into modulating IX properties through structural adjustments in vdWHs.
• The classification of self-trapped IXs offers a potential explanation for diverse experimental spectral observations.