2008
DOI: 10.1103/physrevlett.101.257402
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Photoluminescence Ring Formation in Coupled Quantum Wells: Excitonic Versus Ambipolar Diffusion

Abstract: In this Letter, we study the diffusion properties of photoexcited carriers in coupled quantum wells around the Mott transition. We find that the diffusion of unbound electrons and holes is ambipolar and is characterized by a large diffusion coefficient, similar to that found in p-i-n junctions. Correlation effects in the excitonic phase are found to significantly suppress the carriers' diffusion. We show that this difference in diffusion properties gives rise to the appearance of a photoluminescence ring patte… Show more

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Cited by 41 publications
(41 citation statements)
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“…The emission pattern has two maxima around the excitation spot and is nearly symmetric relative to the excitation spot position. This pattern is similar to the inner ring studied previously [Butov et al, 2002;Ivanov et al, 2006;Alloing et al, 2012;Stern et al, 2008;Ivanov et al, 2010]. The inner ring was explained in terms of exciton transport and cooling: optical excitation heats the exciton gas, excitons cool towards the lattice temperature as they travel away from the excitation spot, the cooling results in an increase in the occupation of the low-energy optically active exciton states and, as a result, the appearance of an emission ring around the excitation spot [Butov et al, 2002;Ivanov et al, 2006;Alloing et al, 2012;Ivanov et al, 2010].…”
Section: Experimental Methodssupporting
confidence: 84%
“…The emission pattern has two maxima around the excitation spot and is nearly symmetric relative to the excitation spot position. This pattern is similar to the inner ring studied previously [Butov et al, 2002;Ivanov et al, 2006;Alloing et al, 2012;Stern et al, 2008;Ivanov et al, 2010]. The inner ring was explained in terms of exciton transport and cooling: optical excitation heats the exciton gas, excitons cool towards the lattice temperature as they travel away from the excitation spot, the cooling results in an increase in the occupation of the low-energy optically active exciton states and, as a result, the appearance of an emission ring around the excitation spot [Butov et al, 2002;Ivanov et al, 2006;Alloing et al, 2012;Ivanov et al, 2010].…”
Section: Experimental Methodssupporting
confidence: 84%
“…10,13,24,27 A set of exciton transport phenomena was observed, including the transistor effect for excitons, 14,15,19,21 localizationdelocalization transition in random potentials 7,9,10,13,17,22 and in static and moving lattices, 18,23,29 and the inner ring in emission patterns. 7,9,17,18,26,28,29,32 The studies of the latter form the subject of this work.…”
Section: Introductionmentioning
confidence: 99%
“…Inter-layer excitons (IXs) in hetero-bilayers of transition metal dichalcogenides (TMDs) [7][8][9][10][11][12][13][14] represent an exciting emergent class of long-lived dipolar composite bosons in an atomically thin, near-ideal two-dimensional (2D) system [5,9,14]. The emergence of quantum correlations in finite 2D systems may open up tantalizing prospects of excitonic Bose-Einstein condensation [5,[14][15][16] and Wigner-crystal like phases[4] at sufficiently low temperatures and in confined geometries [17].Here, we trap a tunable number of dipolar IXs (N IX ∼ 1 − 4) within a nanoscale confinement potential induced by placing a MoSe 2 -WSe 2 hetero-bilayer (HBL) onto an array of SiO 2 nanopillars [18,19]. We control the mean occupation of the IX trap via the optical excitation level and observe discrete sharp-line emission from different configurations of interacting IXs.…”
mentioning
confidence: 99%