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Exciton
About: Exciton is a research topic. Over the lifetime, 31603 publications have been published within this topic receiving 810642 citations.
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TL;DR: Recent studies of semiconductor bilayer systems that provide clear evidence for exciton condensation in the quantum Hall regime are reviewed and why this phenomenon is as likely to occur in electron–electron bilayers as in electron-hole bilayers is explained.
Abstract: An exciton is the particle-like entity that forms when an electron is bound to a positively charged 'hole'. An ordered electronic state in which excitons condense into a single quantum state was proposed as a theoretical possibility many years ago. We review recent studies of semiconductor bilayer systems that provide clear evidence for this phenomenon and explain why exciton condensation in the quantum Hall regime, where these experiments were performed, is as likely to occur in electron–electron bilayers as in electron–hole bilayers. In current quantum Hall excitonic condensates, disorder induces mobile vortices that flow in response to a supercurrent and limit the extremely large bilayer counterflow conductivity.
605 citations
TL;DR: In this article, the 1Se,h−1Pe,h and 1Pe, h−1De,h intraband excitations were identified and assigned to the sub-μs lifetime and near-unity quantum yield.
Abstract: PbSe nanocrystal colloids exhibit a well-defined excitonic structure with the lowest energy exciton tuning from 0.5 to 1 eV, as a function of size. Band-edge fluorescence is observed from 1.2 to 2 μm with a small Stokes shift, sub-μs lifetime, and near-unity quantum yield. Upon pumping at 1.064 μm, the first exciton decay is consistent with radiative relaxation at low pump intensity and with Auger recombination at higher pump intensities. Optically induced absorption is observed at approximately midgap. These transitions exhibit strengths similar to the interband exciton and are size-tunable. They are assigned to the 1Se,h−1Pe,h and 1Pe,h−1De,h intraband excitations. Intraband pump−probe measurements of the 1Se,h−1Pe,h transition reveal a short lifetime and the absence of the phonon bottleneck.
603 citations
IBM1
TL;DR: It is found that simple scaling relationships give a good description of the binding energy, exciton size, and oscillator strength of excitons in nanotubes embedded in a dielectric.
Abstract: Light emission from carbon nanotubes is expected to be dominated by excitonic recombination. Here we calculate the properties of excitons in nanotubes embedded in a dielectric, for a wide range of tube radii and dielectric environments. We find that simple scaling relationships give a good description of the binding energy, exciton size, and oscillator strength.
601 citations
TL;DR: Combinatorial laser molecular-beam epitaxy method was employed to fabricate epitaxial ZnO thin films doped with all the 3d transition metal (TM) ions in a high throughput fashion as discussed by the authors.
Abstract: Combinatorial laser molecular-beam epitaxy method was employed to fabricate epitaxial ZnO thin films doped with all the 3d transition metal (TM) ions in a high throughput fashion The solubility behavior of TM ions was discussed from the viewpoints of the ionic radius and valence state The magneto-optical responses coincident with absorption spectra were observed for Mn- and Co-doped samples Cathodoluminescence spectra were studied for Cr-, Mn-, Fe-, and Co-doped samples, among which Cr-doped ZnO showed two sharp peaks at 297 eV and 371 eV, respectively, at the expense of the exciton emission peak of pure ZnO at 325 eV Different magnetoresistance behavior was observed for the samples codoped with n-type carriers Ferromagnetism was not observed for Cr- to Cu-doped samples down to 3 K
587 citations
TL;DR: It is proved that ultrafast transfer of electrons from MoSe2 to MoS2 layers, despite the strong Coulomb attraction from the holes in the resonantly excited excitons, can be accomplished on an ultrafast time scale, as observed by measuring the differential reflection of a probe tuned to theMoSe2 resonance.
Abstract: We observe subpicosecond charge separation and formation of indirect excitons a van der Waals heterostructure formed by molybdenum disulfide and molybdenum diselenide monolayers. The sample is fabricated by manually stacking monolayer MoS2 and MoSe2 flakes prepared by mechanical exfoliation. Photoluminescence measurements confirm the formation of an effective heterojunction. In the transient absorption measurements, an ultrafast laser pulse resonantly injects excitons in the MoSe2 layer of the heterostructure. Differential reflection of a probe pulse tuned to the MoS2 exciton resonance is immediately observed following the pump excitation. This proves ultrafast transfer of electrons from MoSe2 to MoS2 layers, despite the strong Coulomb attraction from the holes in the resonantly excited excitons. Conversely, when excitons are selectively injected in MoS2, holes transfer to MoSe2 on an ultrafast time scale, too, as observed by measuring the differential reflection of a probe tuned to the MoSe2 resonance. T...
585 citations