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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/{Gamma} 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.
We report the direct observation of intervalley exciton between the Q conduction valley and $Gamma$ valence valley in bilayer WSe$_2$ by photoluminescence. The Q$Gamma$ exciton lies at ~18 meV below the QK exciton and dominates the luminescence of bi
We study the unitary propagation of a two-particle one-dimensional Schrodinger equation by means of the Split-Step Fourier method, to study the coherent evolution of a spatially indirect exciton (IX) in semiconductor heterostructures. The mutual Coul
Emergent quantum phases driven by electronic interactions can manifest in materials with narrowly dispersing, i.e. flat, energy bands. Recently, flat bands have been realized in a variety of graphene-based heterostructures using the tuning parameters
Spin transport of indirect excitons in GaAs/AlGaAs coupled quantum wells was observed by measuring the spatially resolved circular polarization of exciton emission. Exciton spin transport over several microns originates from a long spin relaxation time and long lifetime of indirect excitons.
We demonstrate experimental proof of principle for a stirring potential for indirect excitons. The azimuthal wavelength of this stirring potential is set by the electrode periodicity, the amplitude is controlled by the applied AC voltage, and the angular velocity is controlled by the AC frequency.