Every-other-layer dipolar excitons in a spin-valley locked superlattice

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Optics

Background:

• Monolayer transition metal dichalcogenides (TMDs) exhibit broken inversion symmetry and strong spin-orbit coupling.
• This leads to a spin-valley locking effect, crucial for exotic electronic properties in stacked TMD multilayers.

Purpose of the Study:

• To investigate the nature of excitons in spin-valley locked superlattices formed by 2H stacked TMDs.
• To characterize the optical properties and energy landscape of these novel excitons.

Main Methods:

• Theoretical analysis of electronic superlattices in 2H TMD multilayers.
• Optical spectroscopy (reflectance spectra) to probe exciton behavior.
• Tuning of exciton resonance using electric fields.

Main Results:

• Identification of a dipolar exciton with spatially separated electron-hole pairs in alternating layers.
• Observation of optically bright excitons through hybridization with intralayer excitons.
• Spectroscopic evidence of anti-crossing patterns and an excited state orbital, indicating significant binding energy.

Conclusions:

• The spin-valley locked superlattice in TMDs hosts a unique every-other-layer dipolar exciton.
• This exciton becomes optically active and possesses a substantial binding energy.
• With increasing layer thickness, these excitons can form one-dimensional Bose-Hubbard chains with layer-dependent spectral features.