Spatially indirect intervalley excitons in bilayer WSe2

Abstract

Spatially indirect excitons with displaced wavefunctions of electrons and holes play a pivotal role in a large portfolio of fascinating physical phenomena and emerging optoelectronic applications, such as valleytronics, exciton spin Hall effect, excitonic integrated circuit and high-temperature superfluidity. Here, we uncover three types of spatially indirect excitons (including their phonon replicas) and their quantum-confined Stark effects in hexagonal boron nitride encapsulated bilayer WSe2, by performing electric field-tunable photoluminescence measurements. Because of different out-of-plane electric dipole moments, the energy order between the three types of spatially indirect excitons can be switched by a vertical electric field. Remarkably, we demonstrate, assisted by first-principles calculations, that the observed spatially indirect excitons in bilayer WSe2 are also momentum-indirect, involving electrons and holes from Q and K/Γ valleys in the Brillouin zone, respectively. This is in contrast to the previously reported spatially indirect excitons with electrons and holes localized in the same valley. Furthermore, we find that the spatially indirect intervalley excitons in bilayer WSe2 can exhibit considerable, doping-sensitive circular polarization. The spatially indirect excitons with momentum-dark nature and highly tunable circular polarization open new avenues for exotic valley physics and technological innovations in photonics and optoelectronics.

14 pages, 4 figures

References in corpus (12)

• Observation of Long-Lived Interlayer Excitons in Monolayer MoSe2-WSe2 Heterostructures
• k.p theory for two-dimensional transition metal dichalcogenide semiconductors
• Evidence of high-temperature exciton condensation in 2D atomic double layers
• High-temperature superfluidity with indirect excitons in van der Waals heterostructures
• Valley Phonons and Exciton Complexes in a Monolayer Semiconductor
• Emerging Photoluminescence from the Dark-Exciton Phonon Replica in Monolayer WSe2
• Multipath optical recombination of intervalley dark excitons and trions in monolayer WSe${}_2$
• Exciton dynamics in WSe2 bilayers
• Intrinsic Donor-Bound Excitons in Ultraclean Monolayer Semiconductors
• Electric-field-tunable intervalley excitons and phonon replicas in bilayer WSe${}_2$
• Dipolar excitonic insulator in a moire lattice
• Optically and magnetically addressable valley pseudospin of interlayer excitons in bilayer MoS2

Cited by in corpus (12)

• Electrical control of hybrid exciton transport in a van der Waals heterostructure
• Electrical tuning of moiré excitons in MoSe${}_2$ bilayers
• Stacking-dependent exciton multiplicity in WSe${}_2$ bilayers
• Signatures of electric field and layer separation effects on the spin-valley physics of MoSe${}_2$/WSe${}_2$ heterobilayers: from energy bands to dipolar excitons
• Electrically tunable dipolar interactions between layer-hybridized excitons
• Impact of atomic reconstruction on optical spectra of twisted TMD homobilayers
• Electrically tunable layer-hybridized trions in doped WSe${}_2$ bilayers
• Polarization and charge-separation of moiré excitons in van der Waals heterostructures
• Two dimensional semiconductors: optical and electronic properties
• Brightening interlayer excitons by electric-field-driven hole transfer in bilayer WSe2
• Robust Interlayer Exciton Interplay in Twisted van der Waals Heterotrilayer on a Broadband Bragg Reflector up to Room Temperature
• Measurements of absolute bandgap deformation-potentials of optically-bright bilayer WSe${}_2$