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Hassan Lamsaadi, Aurelien Cuche, Gonzague Agez, Ioannis Paradisanos, Dorian Beret, Laurent Lombez, Pierre Renucci, Delphine Lagarde, Xavier Marie, Ziyang Gan, Antony George, [Kenji Watanabe](https://orcid.org/0000-0003-3701-8119), [Takashi Taniguchi](https://orcid.org/0000-0002-1467-3105), Andrey Turchanin, Nicolas Combe, Bernhard Urbaszek, Vincent Paillard, Jean‐Marie Poumirol

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[Exciton Collimation, Focusing and Trapping Using Complex Transition Metal Dichalcogenide Lateral Heterojunctions](https://mdr.nims.go.jp/datasets/819ce44f-3564-4afd-b287-c54f19e19d2c)

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Exciton Collimation, Focusing and Trapping Using Complex Transition Metal Dichalcogenide Lateral HeterojunctionsRESEARCH ARTICLEwww.advopticalmat.deExciton Collimation, Focusing and Trapping Using ComplexTransition Metal Dichalcogenide Lateral HeterojunctionsHassan Lamsaadi, Aurelien Cuche, Gonzague Agez, Ioannis Paradisanos, Dorian Beret,Laurent Lombez, Pierre Renucci, Delphine Lagarde, Xavier Marie, Ziyang Gan,Antony George, Kenji Watanabe, Takashi Taniguchi, Andrey Turchanin, Nicolas Combe,Bernhard Urbaszek, Vincent Paillard, and Jean-Marie Poumirol*Controlling the motion of neutral excitons in optically active media is amandatory development to enable the conception of advanced circuits anddevices for applications in excitronics, quantum photonics, andoptoelectronics. Recently, proof of unidirectional exciton transport from high-to low-bandgap material is evidenced using a high-quality lateralheterostructure separating transition metal dichalcogenide monolayers(TMD-MLs). In this paper, by combining room-temperaturemicro-photoluminescence far-field imaging with a statistical description ofexciton transport, the underlying excitonic local distribution and fluxes takingplace near lateral heterojunctions are unveiled. The complex 2D excitonictransport properties found near a linear interface separating WSe2 fromMoSe2 TMD-MLs are studied and reveal two distinct diffusion regimesprofoundly affecting the effective diffusion length. Then, it is shown thatcombining two and three of these interfaces, allows advanced in-plane controlof the excitonic distribution and flux over large distances. Exciton focalizationand trapping, allowing an increase in the local exciton density up to threeorders of magnitude are demonstrated. Finally, flux collimation is achievedwith the formation of parallel current lines extending a few micrometers awayfrom the source. We believe that the deterministic shaping and positioning ofthe exciton distribution and flux shown here will be key toward the conceptionof realistic excitronic devices.H. Lamsaadi, A. Cuche, G. Agez, N. Combe, V. Paillard, J.-M. PoumirolCEMES-CNRSUniversité de Toulouse29 Rue Jeanne Marvig, Toulouse 31055, FranceE-mail: jean-marie.poumirol@cemes.frI. ParadisanosInstitute of Electronic Structure and LaserFoundation for Research and Technology-HellasHeraklion 70013, GreeceThe ORCID identification number(s) for the author(s) of this articlecan be found under https://doi.org/10.1002/adom.202403009© 2024 The Author(s). Advanced Optical Materials published byWiley-VCH GmbH. This is an open access article under the terms of theCreative Commons Attribution License, which permits use, distributionand reproduction in any medium, provided the original work is properlycited.DOI: 10.1002/adom.2024030091. IntroductionAtomically-thin semiconductors have beenat the center of a very active research fieldin recent years thanks to their remarkableoptical properties. In particular, transitionmetal dichalcogenide monolayers (TMD-MLs) exhibit a strong Coulomb interaction,resulting in the formation of tightly boundneutral excitons that are highly stable evenat room temperature.[1–5] Furthermore, ex-citons in TMD-MLs allow optical signalsto be encoded and stored in the excitonenergy, spin, valley, and orbital degrees offreedom,[6,7] and they can propagate overhundreds of nanometers before recombin-ing. As a result, TMD-MLs provide an idealplatform for investigating exciton trans-port phenomena and are very promisingcandidates to be used in many quantumphotonic and optoelectronic applications.Excitronic circuits, similar to electroniccircuits, using excitons as active infor-mation carriers have been anticipated tocontrol excitonic states with applied elec-tric and magnetic fields.[8,9] In addition,D. Beret, L. Lombez, P. Renucci, D. Lagarde, X. MarieUniversité de ToulouseINSA-CNRS-UPS, LPCNO135 Avenue Rangueil, Toulouse 31077, FranceZ. Gan, A. George, A. TurchaninFriedrich Schiller University JenaInstitute of Physical Chemistry07743 Jena, GermanyA. George, A. TurchaninAbbe Centre of Photonics07745 Jena, GermanyK. WatanabeResearch Center for Functional MaterialsNational Institute for Materials Science1-1 Namiki, Tsukuba 305-0044, JapanT. TaniguchiInternational Center for Materials NanoarchitectonicsNational Institute for Materials Science1-1 Namiki, Tsukuba 305-0044, JapanAdv. Optical Mater. 2025, 13, 2403009 2403009 (1 of 10) © 2024 The Author(s). Advanced Optical Materials published by Wiley-VCH GmbHhttp://www.advopticalmat.demailto:jean-marie.poumirol@cemes.frhttps://doi.org/10.1002/adom.202403009http://creativecommons.org/licenses/by/4.0/http://crossmark.crossref.org/dialog/?doi=10.1002%2Fadom.202403009&domain=pdf&date_stamp=2024-12-25www.advancedsciencenews.com www.advopticalmat.dephoto-excitonic state interactions can directly process optical sig-nals and re-emit light without the need for additional optical-electrical conversions, making them extremely efficient.[10] Nev-ertheless, because of their neutral charge state, controlled spatialmanipulation of neutral exciton fluxes at room temperature us-ing electric or magnetic fields is challenging. Previous studieson manipulating exciton propagation focused mainly on the useof strained TMD-MLs.[11] The strain gradient obtained throughrough nano-structured substrates is used, for example, for exci-ton funneling.[12]Recently, an alternative method based on CVD-grown high-quality in-plane lateral heterostructures, combining TMD-MLswith different excitonic properties, has unveiled several funda-mental behaviors and opened new perspectives.[13–16] For in-stance, a unidirectional exciton flow has been observed inhigh-quality WSe2-MoSe2 lateral heterojunction (LH), forming adiode-like junction (abrupt interface between two TMD-MLs withdifferent band gaps).[17–19]Excitons photo-generated within the larger bandgap TMD-MLnear the interface are effectively drawn into the adjacent lowerbandgap TMD-ML, facilitating their transfer across the junction.In contrast, excitons generated within the lower bandgap TMD-ML are confined and unable to cross the junction.[17] This phe-nomenon has been described using the concept of an excitonicKapitza resistance-like effect, which accounts for a pronounceddiscontinuity in the excitonic distribution at the junction due toexciton drift (for an in-depth discussion, see ref. [19]). This effectis analogous to the Kapitza resistance observed during phonontransfer across ideal interfaces between two materials, where atemperature discontinuity similarly emerges at the interface.Similar behavior has been observed in WS2𝜉Se2 − 2𝜉 alloy withgradually changing composition 𝜉, where the slowly varying exci-ton energy generates an anisotropic exciton drift and an increas-ing effective diffusion length.[20] However, all those works werefocused on a quasi-1D diffusion observed on straight-line junc-tions. The understanding of how LHs could affect exciton diffu-sion and authorize control of their spatial motion in 2D spaceusing more complex geometries is still lacking.In this work, we go further by demonstrating that TMD-basedlateral heterostructures, depending on their geometry, can pro-foundly modify the trajectory of excitons in a controllable way.This allows complex in-plane manipulation of exciton flux anddistribution. By coupling achromatic μ-photoluminescence (μ-PL) microscopy imaging with homemade numerical simulationtools based on a statistical resolution of the randomly moving ex-citons, we show that a highly directional transfer of kinetic energyto the excitons when transmitted through the junction (from highband gap WSe2 to low band gap MoSe2) or reflected by the junc-tion (from MoSe2 to WSe2) affects both their effective diffusionlengths and trajectories. First, we demonstrate that two differentdiffusion regimes exist in the vicinity of a linear (straight) LH,allowing either i) a strong enhancement of the effective diffusionlength (nearly one order of magnitude) leading to efficient exci-B. UrbaszekInstitute of Condensed Matter PhysicsTechnische Universität Darmstadt64289 Darmstadt, Germanyton transport far away from their source or ii) a regime of forceddiffusion where excitons are forced to move toward high-densityregions, leading to exciton condensation and negative effectivediffusion length. Building on the determined transmission andreflection rules, we study the effect of more complex junctiongeometries near triangular interfaces. We demonstrate that thepresence of two interacting interfaces (near triangular interfaces)generates an excitonic-like lensing effect, allowing, dependingon the position of the exciton source, i) efficient collimation ofthe exciton trajectory or ii) the exciton population to be focusedand concentrated at a controllable position away from the exci-ton source. Finally, we show that a subwavelength-sized MoSe2triangle inclusion in a WSe2 ML drains excitons, thus acting as atrap from the surrounding barrier. The exciton density inside thetrap is increased by nearly three orders of magnitude when thetriangle size is reduced to a few hundred nanometers.2. Results2.1. μ-PL Study of MoSe2-WSe2 LHHigh-quality MoSe2-WSe2 LH is grown using the modified CVDmethod described in ref. [16], then transferred and encapsulatedin hexagonal boron nitride (hBN) on a SiO2/Si substrate (seeMethods in Supporting Information). Following each transferstep, the substrate is annealed at 150°C for 30 min to agglom-erate any nanobubbles away from the junction. We exclusivelyworked with bubble-free junctions to preserve the intrinsic mate-rial properties and eliminate any additional drift of excitons dueto strain from nanobubbles.[21] Figure 1a shows an optical im-age of the sample, with the top and bottom hBN flakes indicatedby the orange and black lines, respectively. The top and bottomcolor maps in Figure 1b represent the normalized maxima of μ-PL and μ-Raman intensities, respectively. A star-shaped MoSe2inclusion (purple) surrounded by WSe2 monolayer (pink) can beidentified. The sample exhibits very few visible defects, mainly bi-layer MoSe2 inclusions at the center of the stars. Figure 1c illus-trates the general atomic configuration at the vicinity of the junc-tion, with the two pure materials WSe2 (pink) and MoSe2 (purple)separated by a junction of width w. The junction is considered tobe formed of a Mo𝜉W1 − 𝜉Se2 alloy with a continuous but abruptlyvarying composition from MoSe2 (left) to WSe2 (right), resultingin a continuously and abruptly varying exciton energy profile asdescribed by Figure 1c.[22] As it will be discussed later, the exactnature of the junction is not crucial for the description of ourexperimental results, as in our case we studied abrupt junctions(narrow width w < 10 nm).To determine the effect of the junction on the exciton diffusion,we performed μ-PL imaging experiments, sequentially imagingthe PL emission pattern and analyzing the collected light with aspectrometer. Figure 1d shows an illustration of the experimen-tal setup. We point out that the laser is tightly focused through ahigh numerical aperture (NA = 0.9), and the emitted light is col-lected by the same objective through a confocal hole of control-lable size (see Methods in Supporting Information). All measure-ments were made at low power density (below 1 × 109 W cm−2) toensure that the excitonic diffusion regime is linear.[19] Figure 2aupper row depicts the μ-PL images for six selected positions ofthe laser excitation recorded along a line perpendicular to theAdv. Optical Mater. 2025, 13, 2403009 2403009 (2 of 10) © 2024 The Author(s). Advanced Optical Materials published by Wiley-VCH GmbH 21951071, 2025, 10, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.202403009 by National Institute For, Wiley Online Library on [01/12/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advopticalmat.dewww.advancedsciencenews.com www.advopticalmat.deFigure 1. μ-PL and μ-Raman characterization of the sample. a) Opticalimage of the hBN/TMD-LH/hBN stack. The top hBN flake boundaries areindicated by the orange solid line (the bottom hBN flake covers the wholeimage, delimited by the black rectangle). The dashed cyan lines show thelateral heterojunctions between a star-shaped MoSe2 monolayer embed-ded in a WSe2 monolayer. b) Top and bottom color maps represent the nor-malized maxima of μ-PL and μ-Raman intensities, respectively. The colormaps are taken inside the square zone (dashed black line) in a. The pur-ple (pink) color corresponds to the MoSe2 (WSe2) signal. c) Schematicrepresentation of an abrupt MoSe2-WSe2 LH showing a thin interface (ofwidth w) with a continuous varying alloy composition, where the excitonenergy continuously increases from the exciton energy inside MoSe2 tothe exciton energy inside WSe2. d) Illustration of the μ-PL imaging set-up.MoSe2-WSe2 LH. As a guide for the eyes and for clarity, the laserspot is indicated by the dashed red circle with a diameter equalto the experimentally measured full width at half maximum,FWHM∼1 μm. The corresponding μ-PL spectra appear inFigure 2b. In Figure 2a, panels (1) and (6) show μ-PL imageswith the laser spot far from the junction, corresponding to thepure exciton emission of MoSe2 and WSe2, respectively. Thisis confirmed by the spectral signatures. For MoSe2 (panel (1)of Figure 2b), the spectrum corresponds to the neutral excitonAMoSe21s centered around ∼1.57 eV (FWHM ≈ 50 meV). For WSe2(panel (6) of Figure 2b), an asymmetric spectrum exhibits thecontribution of the dark exciton XD centered ≈1.62 eV (FWHM≈ 30 meV), in addition to the dominant feature of the neutral ex-citon AWSe21s centered around ≈1.66 eV (FWHM ≈ 40 meV).[23–25]In addition, WSe2 is much brighter than MoSe2 (≈3 times), andboth patterns reveal a clear isotropic diffusion in each material,with the μ-PL intensity maximum position matching the laser ex-citation center. This is confirmed by the 1D profiles taken fromthe corresponding μ-PL images (panels 1 and 6) presented inFigure 2a lower row. Those profiles show the variation along thex-axis of the integrated intensity (IPL(x, xlaser) = ∫dyIPL(x, y, xlaser)),calculated by integrating along the y-axis the μ-PL intensity of the2D maps (IPL(x, y, xlaser)). This is in agreement with symmetricexciton effective diffusion lengths of LWSe2D ∼ 90 nm and LMoSe2D ∼142 nm, aligned with the previous studies on the same kind ofsamples.[17,19]A very interesting and complex behavior takes place whenmoving the laser across the junction from MoSe2 to WSe2 (pan-els 2 to 5 in Figure 2a). The intensity pattern is strongly mod-ified depending on the relative position of the laser excitationwith respect to the junction (Figure S1, Supporting Informationillustrates the method used to estimate the junction position). Inpanel (2), only the laser spot edge is illuminating the junction,but a sensitive increase of the PL pattern broadening along thex-axis toward WSe2 can be seen (especially compared to the laserspot size), a sign of an enhanced effective diffusion length alongthat direction. In panel (3), the broadening is further increased,with the appearance of two distinct maxima. One of them nearlymatches the position of the laser excitation center, while the othermaximum appears near the position of the junction, making theμ-PL intensity pattern strongly asymmetric. To quantify the spa-tial broadening of the PL distribution, we use the Full Width atOuter Half Maximum (FWOHM), defined as the distance be-tween the outermost points where the intensity drops to half ofthe maximum value, providing a robust measure applicable toboth unimodal and bimodal distributions. In the configuration(3), the FWOHM of the μ-PL spot is reaching 1500 nm, ≈1.5times larger than the one observed in (1) and (6). In panel (4),we emphasize that the asymmetry of the μ-PL intensity patternis further increased, and that the PL intensity maximum is nolonger matching the laser center. It is shifted by ≈400 nm alongthe x-axis toward the WSe2 side of the junction, while a shoulderis still visible deep inside the MoSe2 side. When further increas-ing the proportion of laser excitation occurring inside WSe2 (laserspot center close to the junction as in panel (5)), an abrupt changeof the μ-PL intensity pattern is observed: the maximum of the μ-PL intensity is still pushed away from the junction (by ≈150 nm),and the PL spot shrinks to a size smaller than the laser excitationAdv. Optical Mater. 2025, 13, 2403009 2403009 (3 of 10) © 2024 The Author(s). Advanced Optical Materials published by Wiley-VCH GmbH 21951071, 2025, 10, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.202403009 by National Institute For, Wiley Online Library on [01/12/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advopticalmat.dewww.advancedsciencenews.com www.advopticalmat.deFigure 2. μ-PL imaging experiment of exciton diffusion through MoSe2-WSe2 LH. a) Top panels: μ-PL images measured away from the junction inMoSe2 (1) and in WSe2 (6), and close to the junction (2 to 5). The dashed red circle, with a diameter of FWHM ∼ 1μm, indicates the position of theexcitation laser spot, and the dashed purple line indicates the estimated position of the junction separating MoSe2 and WSe2. The pixels appearing onthe images are the actual pixels of the camera used to image the μ-PL. Bottom panels: x-axis profiles taken from the corresponding intensity maps. Bluecurves: integrated μ-PL intensity IPL(x, xlaser) = ∫dyIPL(x, y, xlaser); red curves: integrated intensity profile of the laser spot (Ilaser(x) = ∫dyIlaser(x, y)). b) μ-PLspectra measured at positions (1) to (6). Insets: illustration of different exciton transitions in MoSe2 and WSe2. c) Color map obtained from plottingthe integrated μ-PL intensity IPL(x, xlaser) = ∫dyIPL(x, y, xlaser)) profiles (as displayed in a bottom panels) as a function of the position of the excitationsource (center of the laser spot shown by the diagonal dotted red line), the dotted black line shows the position of the integrated intensity maximum.The vertical dashed line represents the separation between the two materials. d. Same as c but for integrated μ-PL intensity IPL(y, xlaser) = ∫dxIPL(x, y,xlaser). e Full Width at Outer Half Maximum (FWOHM) of the integrated intensity profiles IPL(x, xlaser) (red) and IPL(y, xlaser) (blue) as a function of theposition of the laser center. FWOHM is defined as the distance between the outermost points where the intensity drops to half of the maximum.profile. Note that the behavior described here is typical andappears when scanning other junctions on the sample (seeFigure S2a, Supporting Information).Except for positions (1) and (6) far from the junction, the spec-tra measured on all other positions (see Figure 2b) show bothsignatures of WSe2 and MoSe2 materials, with various intensityratio, which means that excitons are recombining on each sideof the junction. It is interesting to note that neither AWSe21s norAMoSe21s energy and broadening are affected by the presence of thejunction. This is a good indication that the junction is very sharp,and the alloying region between the two materials, if any, is verysmall (in agreement with TEM image shown in ref. [17]). Fur-thermore, as the laser excitation approaches the junction fromAdv. Optical Mater. 2025, 13, 2403009 2403009 (4 of 10) © 2024 The Author(s). Advanced Optical Materials published by Wiley-VCH GmbH 21951071, 2025, 10, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.202403009 by National Institute For, Wiley Online Library on [01/12/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advopticalmat.dewww.advancedsciencenews.com www.advopticalmat.deMoSe2 side, the PL intensity of MoSe2 nearly triples before goingto zero when the excitation laser takes place exclusively insideWSe2 (see PL spectra in Figure 2c). This increase of MoSe2 PLintensity confirms that the junction efficiently drives and accel-erates excitons toward MoSe2.[19] Finally, as expected for roomtemperature measurements, no signature of charge transfer ex-citons can be detected.[26]To go further and confirm that the local exciton density canbe strongly modified near the junction and that this modifica-tion occurs only in the direction perpendicular to the junction,the color map in Figure 2c gives the integrated intensity profilesIPL(x, xlaser) = ∫dyIPL(x, y, xlaser) as a function of the laser position.Unambiguously, close to the interface, the PL spot splits into twopeaks, generalizing the results shown in the six profiles displayedin Figure 2a. In contrast, the color map in Figure 2d showing theintegrated intensity profiles IPL(y, xlaser) = ∫dxIPL(x, y, xlaser) ex-hibits a single maximum always matching the laser center, prov-ing that the junction does not influence the exciton distributionalong the y-axis. Figure 2e shows the experimental FWOHM ofthe μ-PL spot. The red curve (blue curve) displays the FWOHMalong the x-direction (y-direction). One can clearly see that, nearthe junction, two areas with very different diffusion regimes ap-pear. First, an enhanced effective diffusion regime, where theFWOHM of the PL spot along the x-axis (red curve) is stronglyincreased by up to 50% compared to the y-axis FWOHM (bluecurve), effectively spreading the PL spot. Second, a forced effec-tive diffusion regime, where the FWOHM of the PL spot alongthe x-axis now becomes smaller than the one measured alongthe y-axis (the red curve going above the blue curve). The mea-sured FWOHM goes down to 800 nm, meaning that along thex-direction, the μ-PL spot is smaller than the laser spot which isvery surprising and cannot be explained without accounting fora strongly an-isotropic diffusion.2.2. Statistical Approach of Exciton DiffusionIn this section, we develop a model that describes the effect of thejunction on the exciton distribution to explain the complex be-havior of the experimental μ-PL profile described above. We usea statistical approach to solve, in the linear regime, the following2D diffusion equation:−⃖⃖⃗∇.(−D(r)⃖⃖⃗∇n(r, rs, t) + v⃗∗(r)n(r, rs, t))−n(r, rs, t)𝜏(r)+ Γ(r, rs) =𝜕n(r, rs, t)𝜕t(1)where n(r, rs, t) represents the time-dependent exciton densityat the r(x, y) position with the excitation source centered at thers(xlaser, ylaser) position. D(r) and 𝜏(r) are the intrinsic diffusion co-efficient and lifetime of exciton, respectively.In the left-hand side of Equation 1, the first term−D(r)⃖⃖⃗∇n(r, rs, t) represents the diffusion flux and v⃗∗(r)n(r, rs, t)the drift flux through the junction. Indeed, the exciton reachingthe junction acquires a velocity directed from the high-bandgapmaterial toward the low-bandgap material and related to itsenergy-variation, ΔE = EWSe2− EMoSe2. We assume for the pur-pose of the model that the exciton energy varies continuouslyfollowing Vegard’s law with varying alloy concentrations insidethe interface region over a distance w that can be adjusteddepending on the abruptness of the simulated junction (seeMethods in Supporting Information for more details and gener-alizations). Inside relatively abrupt junctions, corresponding toour experimental case, the drift velocity can be approximated by:v⃗∗(x, y) ≃ ⃖⃖⃗v0∗(w)(1 + xΞ), 0 ≤ x ≤ w (2)where ⃖⃖⃗v0∗(w) = − 𝜇w(ΔE − bg )x̂ is the drift velocity at the origin ofthe x axis (Refer to the frame (x̂, ŷ) in Figure 1b), μ is the excitonmobility inside the interface, bg is the band gap bowing param-eter (see Methods in Supporting Information for details) and x̂is the unit vector along the x-direction. The characteristic bow-ing distance is denoted by Ξ = w(ΔE − bg)/(2bg). Finally, on theleft-hand side of Equation (1), the second and last term repre-sent the recombination rate per time unit and the exciton photo-generation rate Γ (per unit of area and unit of time), respec-tively. The photo-generation rate spatial dependence is approxi-mated by a 2D Gaussian profile, mimicking the laser excitationprofile.The steady-state exciton density in each position can be calcu-lated as the excitation laser approaches the junction. However, inorder to directly compare the theoretical predictions with experi-ments, we calculated the μ-PL images by convoluting the excitondensity by a microscope objective-related Gaussian point spreadfunction (PSF) (see Methods in Supporting Information for de-tails), related to the diffraction-limited spatial resolution of theobjective at the emission wavelength. Figure 3a–e are the theoret-ical counterparts of the experimental results given in Figure 2a–e.Figure 3a top row thus shows the calculated μ-PL intensity pat-terns for the laser and junction positions that match the ex-perimental ones. Figure 3a in the bottom row presents the in-tegrated intensity profiles along the x-axis (red curves), calcu-lated from the maps as the experimental profiles of Figure 2a.Notice that exciton density profiles are added (blue curves). Tomatch the experimental observations mentioned above, the the-oretical width of the heterojunction was chosen to be very nar-row (w = 3 nm). We set intrinsic diffusion coefficients and life-times in Equation 1 to the experimental effective values mea-sured at room temperature by time-resolved PL spectroscopy(TRPL)[17,19,27]: DWSe2≃ 1 cm2.s−1, DMoSe2≃ 4 cm2.s−1, 𝜏WSe2≃ 80ps and 𝜏MoSe2≃ 50 ps. Finally, to match the relative integrated PLintensity ratio observed experimentally (see Figure 2b), the ratioof exciton generation rate amplitude is set as ΓWSe20 = 3ΓMoSe20 . Todecrease the number of free parameters accounted for the simu-lation, we fixed the thin interface properties by setting averagedvalues: Dinterface ≃ (DMoSe2+ DWSe2)∕2, 𝜏interface ≃ (𝜏MoSe2+ 𝜏WSe2)∕2and Γinterface0 = (ΓWSe20 + ΓMoSe20 )∕2. This choice of approximationis supported by previous studies that suggest that in such high-quality and sharp junctions, no drastic changes in diffusion pa-rameters are expected.[17–20]One can clearly see that both experimental (Figure 2a) and the-oretical (Figure 3a) images are in excellent agreement. All thepreviously described modifications of the μ -PL intensity patternslinked to the junction (shape, FWOHM, number of maxima andamplitude) are captured by the model. The progressive increasein broadening and the appearance of two distinct peaks of varyingamplitude can be seen in positions (2), (3), and (4). The abruptshrinkage of the spot size and the shift in position (5) are also wellreproduced. Figures 3b and c show the color maps obtained fromAdv. Optical Mater. 2025, 13, 2403009 2403009 (5 of 10) © 2024 The Author(s). Advanced Optical Materials published by Wiley-VCH GmbH 21951071, 2025, 10, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.202403009 by National Institute For, Wiley Online Library on [01/12/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advopticalmat.dewww.advancedsciencenews.com www.advopticalmat.deFigure 3. Modeling the exciton diffusion through the junction. a) top row: steady-state μ-PL images matching the experimental image positions (1) to(6), obtained by convolution of the calculated steady-state exciton distribution with an objective-related Gaussian PSF. The dashed red circle, with adiameter of FWHM ∼ 1μm, indicates the position of the excitation laser spot, and the dashed pink line indicates the position of the junction separatingMoSe2 and WSe2; bottom row: integrated μ-PL intensity profiles IPL(x, xlaser) = ∫dyIPL(x, y, xlaser) (red curves) taken from the corresponding intensitymaps, and x-axis profiles of the exciton density n(x, xlaser) = ∫dyn(x, y, xlaser) (blue); the red shaded areas show the laser excitation profile. b) The colormap obtained from the integrated μ-PL intensity IPL(x, xlaser) = ∫dyIPL(x, y, xlaser) profiles as a function of the position of the excitation source (the centerof the laser spot shown by the red dotted line), the vertical dashed line represents the separation between the two materials. Notice the two maximaaround the interface. c) Same as (b) but for μ-PL intensity IPL(y, xlaser) = ∫dxIPL(x, y, xlaser)). d. FWOHMs extracted from the x-axis (red) and y-axis (blue)integrated μ-PL intensity profiles. e. Normalized exciton density color maps were calculated for positions (1), (3), and (5). The colored contours representthe isodensity curves. The white streamlines indicate the orientation of the exciton flux, showing the isotropic diffusion far from the junction (1) to ahighly oriented flux (5). The pink arrow indicates the position of the junction.the theoretical integrated μ-PL intensities profiles IPL(x, xlaser) =∫dyIPL(x, y, xlaser) and IPL(y, xlaser) = ∫dxIPL(x, y, xlaser), respectively.Again, they are in excellent agreement with the experimentalones shown in Figure 2c,d, respectively. This confirms that ourmodel describes very well both exciton diffusion and recombina-tion for any position of the excitation.3. Discussion3.1. One Interface: Exciton Distribution and FluxHaving access to the exciton spatial distribution helps us under-stand how exciton Kapitza resistance at the junction affects theAdv. Optical Mater. 2025, 13, 2403009 2403009 (6 of 10) © 2024 The Author(s). Advanced Optical Materials published by Wiley-VCH GmbH 21951071, 2025, 10, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.202403009 by National Institute For, Wiley Online Library on [01/12/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advopticalmat.dewww.advancedsciencenews.com www.advopticalmat.dePL emission in the optical far field configuration. When exci-tons are approaching the junction, two scenarios occur depend-ing on whether excitons are generated in WSe2 or in MoSe2. Inthe first case, excitons are strongly drifted toward and perpendic-ularly to the junction, while in the second case, they are blockedby this junction. This creates for all calculated configurations astrong discontinuity of the exciton density (see blue profiles inFigure 3a bottom row), which can be described by a very high-density spot situated near the junction on the MoSe2 side and,on the WSe2 side, a mirroring minimum adjacent to the junc-tion followed by a second maximum of exciton density. The mod-ification of the relative amplitude of those three specific densityfeatures depending on the position of the laser source is at theorigin of the observed complex behavior. Figure 3d shows theFWOHM for the integrated intensity profiles calculated on thex-axis (red curve) and y-axis (blue curve) as a function of the po-sition of the excitation source. Compared with the experimentaldata shown in Figure 2e, the model captures very well both thediffusion regimes described above, confirming i) that in the en-hanced diffusion regime, the interaction with the LH results inan enhanced effective diffusion length and ii) that in the forceddiffusion regime, excitons are forced to diffuse toward a smallerarea than the one they are excited in, resulting in an increasein exciton density compared to the isotropic case. However, onecan see that the agreement between experiment and simulation,while still fairly good, is not perfect. In that case, the simulationslightly misses the laser position (xlaser) at which the FWOHMminimum of the x-axis profile takes place. We believe that asthe exciton density strongly increases locally at the junction, bothAuger recombination and emission/reabsorption of hot phononsoccur. This should play a non-negligible role in causing an ex-tra thermal drift of excitons (Seebeck effect),[28] which slightlybroadens the experimental diffusion profiles (compared to thecalculation).Finally, we point out that our model not only describes verywell the experimental results but also gives us access to thesteady-state exciton flux, ⃖⃗𝜙(r, rs) = −D(r)⃖⃖⃗∇n(r, rs), deduced fromthe calculated exciton density, which allows us to predict the ex-citon average trajectories. Figure 3e depicts the normalized ex-citon density color maps for positions (1), (3), and (5). Coloredcontours and white streamlines represent the exciton isodensitycurves and exciton flux orientations, respectively. As expected, farfrom the junction (see color map (1)), the diffusion is isotropic,as shown by both circular isodensity curves and radial flux lines.However, one can see that near the junction, the diffusion is pro-foundly affected. The junction has a significant impact on the ex-citon flux, redirecting it perpendicularly to the junction, and theexciton isodensity curves are no longer circular. In the enhanceddiffusion regime (see color map (3)), it is obvious that the exci-ton flux imposed by the junction creates an exciton distributionpresenting two separated maxima, in agreement with previousobservations such as the μ-PL maxima (Figures 2a and 3a). Oneof the maxima (on the MoSe2 side) is linked to the very high ex-citon generation inside the MoSe2 layer at the center of the laserspot. The second one appears right at the junction on the WSe2side. At this position, the laser power density is much weaker thanat the laser center, but due to the larger exciton generation rateof WSe2, the two maxima are of comparable amplitude. Lookingat the exciton flux distribution, it appears that this splitting ofthe exciton distribution is due to the competition between: i) thejunction generated parallelized exciton flux originating from theWSe2 side and perpendicularly to it (this region with nearly par-allel flux lines extending approximately ≈250 nm away from thejunction), and ii) the diffusion originating from the first hot spotin MoSe2. Those two opposing fluxes block the exciton diffusiontoward the interface area, generating, in the n(r) distribution, alow-intensity saddle point between the two high exciton densityspots. In the forced diffusion regime (see color map (5)), one cansee that the parallelized exciton flux generated by the junction iseven more predominant. As the laser center is now located nearlyat the junction, the above-described competition between two hotspots does not occur, and nearly parallel flux lines are now foundnearly 1μm away from the exciton source. In both described dif-fusion regimes, the exciton flux near the junction is one order ofmagnitude greater than the one calculated away from it.3.2. Two Interfaces: Collimation and FocusingWe now study a more complex interface geometry that is natu-rally found in our samples. The tips of the MoSe2 stars form tri-angles with two tilted junctions, crossing at a 60° angle, as illus-trated in Figure 4a. As the laser excitation crosses the triangularinterface, moving from MoSe2 to WSe2, we obtain μ-PL imagesexperimentally and numerically using our model (two examplesare given for two laser positions in insets of Figure 4b). Note thatthere is no change in energy and broadening of the excitonic con-tributions of each material, confirming a very sharp triangularinterface. The FWOHM of the x- and y-axes profiles of the μ-PLintensity are shown in Figure 4b in red and blue, respectively. Theexperiment (top panel) and theory (bottom panel) are in very goodagreement. Contrary to the behavior described above, where theforced and enhanced diffusion regimes are both found along thex-direction for different positions of the laser center (with verylittle variation along y-direction), here the specific interface ge-ometry projects both phenomena onto the different directions.The forced diffusion regime is now only found along the x-axis,while enhanced diffusion (with FWOHM reaching ≈1.8μm) oc-curs mainly along the y-axis. Note that the triangular structureis more efficient in enhancing the effective diffusion length thanthe straight one, with a PL diffusion spot reaching ≈1.9μm. Theresulting diffusion is therefore even more anisotropic than inthe straight junction, with the possibility of independently affect-ing the effective diffusion length of the x- and y-axis. μ-PL colormaps in insets of Figure 4b and predicted exciton distributionin Figure 4c illustrate clearly this behavior. In configuration 1, adistinct split of the μ-PL spot is visible, with two separate PL hotspots that appear at the interface. The exciton density observedat these two points is high. We point out that the distance be-tween the two hot spots can be controlled, as it depends only onthe distance between the two interfaces. In configuration 2, theFWOHM is reduced along the x -axis while increasing along they -axis resulting in a strongly oblong PL spot.Figure 4c also shows the calculated exciton flux orientation(white streamlines). The exciton flux strongly depends on theposition of the excitation source. Indeed, as excitons are trans-mitted through the junction, their trajectories are modified bythe peculiar geometry of the interface. In configuration 2, theAdv. Optical Mater. 2025, 13, 2403009 2403009 (7 of 10) © 2024 The Author(s). Advanced Optical Materials published by Wiley-VCH GmbH 21951071, 2025, 10, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.202403009 by National Institute For, Wiley Online Library on [01/12/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advopticalmat.dewww.advancedsciencenews.com www.advopticalmat.deFigure 4. Exciton diffusion through a triangular interface. a) A schematic illustration of a triangular interface. The pink dashed lines indicate a thin alloyseparating MoSe2 and WSe2 materials. b) top panel: Experimental FWOHM of the x-axis (red square) and y-axis (blue square) profiles as a function ofthe position of the laser center. The dashed lines are guides for the eyes. Insets show μ-PL images taken near the apex of the MoSe2 triangle at positions1 and 2, with the center of the laser spot being located at the center of the color maps. b) bottom panel: same as the top panel but for simulated μ-PLprofiles. c) Calculated exciton distribution and exciton flux orientation for a triangular junction with the laser source placed at positions 1 and 2 shownin (b) bottom panel.laser is placed at the triangle apex. As expected, excitons that arenot interacting with the junction are diffusing isotropically withcircular isodensity curves and radial flux lines. In contrast, thetrajectories of excitons approaching the junction are modified asthey acquire an extra component to their velocity perpendicularto the interface. Because of the triangular shape of the interface,excitons transmitted through the bottom and top interfaces arepushed toward the same point in space close to the apex (insideMoSe2). In the inset of Figure 4c, this is clearly visible as a regionof space near the triangular apex, which clearly presents a highdensity of convex isodensity curves, indicating converging trajec-tories leading to an increased exciton density. We would like topoint out that with such a high-density gradient localized at thetriangle apex, the resulting exciton diffusion away from the cor-ner is very efficient. Generating such an exciton distribution atequilibrium is only possible because the junction, by altering theexcitonic flux over large distances, is capable of draining a largenumber of excitons toward this small area.Moving further away to the left from the apex, excitons presentcollimated average trajectories with excitons moving away fromthe source (inside MoSe2) following nearly perfectly parallel aver-age trajectories as far as ≈1.5μm away from the source (up to theleft edge of the color map). Recalling the configuration describedin Figure 3 map (5) that already presented parallelized flux lines,one can see that the triangular interface is much more efficientat maintaining a collimated exciton flux over large distances. Inconfiguration 1, the laser is now centered ≈300 nm inside MoSe2and one can see here a similar feature to the one described abovebut in a less optimal way. Indeed, first, the area of space whereexcitons are pushed together is larger, resulting in a lower localexciton density. Second, looking at the white streamlines awayfrom the source, it is obvious that it is less efficient at convertingthe divergent excitonic trajectories into a set of parallel flux lines.This indicates that controlling the position of the exciton sourcesrelative to the triangular interface tip gives the possibility of tun-ing the degree of divergence of the exciton flux lines.3.3. Three Interfaces: Exciton Funneling and TrappingFinally, the last key feature that we will focus on for this type ofsystem is the ability to trap and confine neutral excitons withina controllable-size area. In fact, the efficient unidirectional ex-citon transport and trapping we demonstrated above suggeststhat a triangle-shaped MoSe2 island surrounded by WSe2 mate-rial should lead to huge amounts of excitons being forced intothe MoSe2 triangle and then trapped inside. Reducing the sizeof a small MoSe2 triangle will then lead to an increasing excitonpopulation that occupies a decreasing area. We performed μ-PLimaging on a small MoSe2 triangle of size inferior to the laserspot size found in our sample (Tip-enhanced Raman characteri-zation is given in Figure 2c). To obtain spatially resolved informa-tion from the μ-PL spectra, and as described in Methods in Sup-porting Information, we added a 75 μm large pinhole. In such aconfiguration, due to the μ-scope magnification, the signal is col-lected only over a circular area of ≈750 nm centered at the laserspot center. In Figure 5a, the blue spectrum is measured withthe pinhole, where only the photons emitted by excitons recom-bining inside a ≈750 nm diameter circle centered on the lasercenter are collected, while the red spectrum corresponds to thespectra measured without the pinhole, where all photons are col-lected independently of the position of emission. One can clearlysee that the contribution of MoSe2 excitons remains the same inboth spectra (the spectra are not re-normalized), indicating firstthat the MoSe2 island is smaller than the area delimited by thecollection and, second, that very few excitons are recombiningAdv. Optical Mater. 2025, 13, 2403009 2403009 (8 of 10) © 2024 The Author(s). Advanced Optical Materials published by Wiley-VCH GmbH 21951071, 2025, 10, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.202403009 by National Institute For, Wiley Online Library on [01/12/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advopticalmat.dewww.advancedsciencenews.com www.advopticalmat.deFigure 5. Exciton trapping in sub-wavelength sized MoSe2 triangles a) μ-PL spectra taken with the laser being centered at the centroid of the MoSe2triangle with the pinhole (blue spectrum) and without the pinhole (red spectrum). b) x-axis profile of the laser intensity (red curve) and μ-PL intensity(green curve) with the excitation laser being centered on the small MoSe2 triangle characterized in Figure S2 (Supporting Information). As a reference,the profile of the isotropic case taken away from the junction inside the MoSe2 is given in blue. c) Calculated average exciton density inside the MoSe2triangle versus the triangle side length with the excitation laser centered at the centroid of the MoSe2 triangle as illustrated in the inset. The color mapsshow the exciton density calculated for cases 1, 2, and 3. For clarity, the three false-color insets are individually normalized.inside WSe2. This is surprising because, due to the small sizeof the MoSe2 island, a non-negligible portion of the laser shinesdirectly on WSe2, seemingly indicating that excitons are beingtrapped inside MoSe2. This is confirmed by the measured inte-grated intensity profiles along the x-axis (measured as describedabove in Section 2.1) plotted in green in Figure 5b, where the μ-PL intensity extends less than the x-axis profile measured in theisotropic case (i.e. away from the junction) inside MoSe2 (bluecurve) and even than the laser excitation profile (red curve), prov-ing that excitons are being forced to diffuse from the excitationinside a smaller MoSe2 triangle, de facto concentrating excitons.To go further, in Figure 5c, we display the expected averageexciton density calculated with our model inside a MoSe2 equi-lateral triangle versus the side length of the triangle (with thelaser-centered on the MoSe2 triangle centroid as illustrated in theinset). A strong increase is evidenced by decreasing the trianglesize, the resulting average exciton density inside the MoSe2 trian-gle is increased by three orders of magnitude when the triangleside is reduced from 2500 to 100 nm. This clearly illustrates theability of the small MoSe2 triangle to drag and trap excitons fromsurrounding WSe2 over large distances. It is interesting to lookat the local exciton distribution as the triangle decreases in size(see insets in Figure 5c). In inset 1, the triangle is of compara-ble size with the laser spot, and the density maxima appear alongthe three edges, with an exciton transport dominated by the en-hanced regime described in Section 1 pushing excitons towardthe triangle centroid. In inset 2, when the triangle edges becomesmaller than ≈1 μm, the maxima of exciton density are moved tothe triangle apexes, with an exciton transport dominated by the“lensing” effect described in Section 2. In inset 1, for a small tri-angle, a more homogeneous exciton distribution is observed ashot spots start to merge. Figure S2d (Supporting Information)shows the same color maps but normalized to the same value.Note that small MoSe2 triangles isolate and homogenize a highdensity of photo-generated excitons, making them a promisingplatform for investigating new collective excitonic effects. Finally,we emphasize that the results shown here are only a proof ofconcept and have inherent limitations. Indeed, as all calculationsare made assuming the linear regime, if the resulting local ex-citon density generated inside the MoSe2 triangle becomes highenough to generate non-negligible non-linear behavior, such asexciton–exciton annihilation, the predicted dependence will nolonger be correct.4. ConclusionIn summary, room-temperature μ-PL imaging on high-qualityWSe2-MoSe2 LH combined with a theoretical study based on astatistical approach of exciton diffusion were performed. In thelow exciton density regime, we shed light on the in-plane exci-ton flux control offered by TMD heteromonolayers. Our workdemonstrates that the abrupt change in exciton energy trans-forms the 2D isotopic diffusion into a strong anisotropic diffu-sion pattern along the direction perpendicular to the junction,drastically affecting the effective diffusion length in a given direc-tion, forcing either excitons to spread over large distances or, onthe contrary, pushing them together to create a high-density hotspot. Going further, we show that combining two of the straightinterfaces to form a triangle can act as an “excitonic lens,” whichis able, for a specific position of the source, to collimate the natu-rally diverging exciton flux into a beam of parallel-propagatingexcitons. Finally, we show that MoSe2 triangles embedded ina WSe2 matrix with sub-wavelength sizes ranging from a fewdozen to a few hundred nanometers are highly efficient systemsfor trapping and confining excitons in adjustable-size spaces.Our findings reveal a set of refraction-like rules that describeglobal changes in global trajectories as a neutral exciton changemedium. We explored experimentally and theoretically three dif-ferent naturally occurring geometries and described the diversepossibilities offered by this type of system. As such, we believethat this work has the potential to open the door to a wide rangeof emerging quantum applications in designing new excitonicAdv. Optical Mater. 2025, 13, 2403009 2403009 (9 of 10) © 2024 The Author(s). Advanced Optical Materials published by Wiley-VCH GmbH 21951071, 2025, 10, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.202403009 by National Institute For, Wiley Online Library on [01/12/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advopticalmat.dewww.advancedsciencenews.com www.advopticalmat.detechnologies, such as new collective excitonic phenomena, ex-citon Bose–Einstein condensate, and exciton quantum dots-based applications.Supporting InformationSupporting Information is available from the Wiley Online Library or fromthe author.AcknowledgementsThis work was financially supported by ANR Ti-P (ANR-21-CE30-0042),the Deutsche Forschungsgemeinschaft (DFG) through a research in-frastructure grant CRC 1375 NOA (Project B2, 398816777), SPP2244(Project TU149/21-1, 443361515) and DFG individual grant TU149/16-1(464283495).Conflict of InterestThe authors declare no conflicts of interest.Data Availability StatementThe data that support the findings of this study are available from thecorresponding author upon reasonable request.Keywordsexciton diffusion, exciton transfer, exciton control, exciton flux, excitonkapitza resistance, excitronics, lateral heterostructure, transition metaldichalcogenideReceived: November 5, 2024Revised: December 6, 2024Published online: December 25, 2024[1] G. Wang, A. Chernikov, M. M. Glazov, T. F. Heinz, X. Marie, T. Amand,B. Urbaszek, Rev. Mod. Phys. 2018, 90, 021001.[2] M. Koperski, M. R. Molas, A. Arora, K. Nogajewski, A. O.Slobodeniuk, C. Faugeras, M. Potemski, Nanophotonics 2017, 6, 1289.[3] D. Y. Qiu, T. Cao, S. G. Louie, Phys. Rev. Lett. 2015, 115, 176801.[4] A. Steinhoff, M. Rosner, F. Jahnke, T. O. Wehling, C. Gies, Nano Lett.2014, 14, 3743.[5] E. Malic, M. Selig, M. Feierabend, S. Brem, D. Christiansen, F.Wendler, A. Knorr, G. Berghäuser, Phys. Rev. Mater. 2018, 2, 014002.[6] R. C. Miller, A. C. Gossard, W. T. Tsang, Phys. B+C 1983, 117-118,714.[7] P. Rivera, H. Yu, K. L. Seyler, N. P. Wilson, W. Yao, X. Xu, Nat. Nan-otechnol. 2018, 13, 1004.[8] A. A. High, E. E. Novitskaya, L. V. Butov, M. Hanson, A. C. Gossard,Science 2008, 321, 229.[9] Y. Chen, W. Yao, Z. Liu, J. Hu, J. Li, D. Li, Adv. Phys. Res. 2023, 2200083.[10] R. Peng, A. Ripin, Y. Ye, J. Zhu, C. Wu, S. Lee, H. Li, T. Taniguchi, K.Watanabe, T. Cao, X. Xu, M. Li, Nat. Commun. 2022, 13, 1334.[11] Y. Hu, F. Zhang, M. Titze, B. Deng, H. Li, G. J. Cheng, Nanoscale 2018,10, 5717.[12] F. Dirnberger, J. D. Ziegler, P. E. Faria Junior, R. Bushati, T. Taniguchi,K. Watanabe, J. Fabian, D. Bougeard, A. Chernikov, V. M. Menon, Sci.Adv. 2021, 7, eabj3066.[13] C. Chakraborty, N. Vamivakas, D. Englund, Nanophotonics 2019, 8,2017.[14] M. Yagmurcukardes, Y. Qin, S. Ozen, M. Sayyad, F. M. Peeters, S.Tongay, H. Sahin, Appl. Phys. Rev. 2020, 7, 1.[15] Y. Liu, N. O. Weiss, X. Duan, H.-C. Cheng, Y. Huang, X. Duan, Nat.Rev. Mater. 2016, 1, 1.[16] E. Najafidehaghani, Z. Gan, A. George, T. Lehnert, G. Q. Ngo, C.Neumann, T. Bucher, I. Staude, D. Kaiser, T. Vogl, et al., Adv. Funct.Mater. 2021, 31, 2101086.[17] D. Beret, I. Paradisanos, H. Lamsaadi, Z. Gan, E. Najafidehaghani, A.George, T. Lehnert, J. Biskupek, U. Kaiser, S. Shree, A. Estrada-Real,D. Lagarde, X. Marie, P. Renucci, K. Watanabe, T. Taniguchi, S. Weber,V. Paillard, L. Lombez, J.-M. Poumirol, A. Turchanin, B. Urbaszek, npj2D Mater. Appl. 2022, 6, 84.[18] M. Shimasaki, T. Nishihara, K. Matsuda, T. Endo, Y. Takaguchi, Z. Liu,Y. Miyata, Y. Miyauchi, ACS nano 2022, 16, 8205.[19] H. Lamsaadi, D. Beret, I. Paradisanos, P. Renucci, D. Lagarde, X.Marie, B. Urbaszek, Z. Gan, A. George, K. Watanabe, T. Taniguchi,A. Turchanin, L. Lombez, N. Combe, V. Paillard, J.-M. Poumirol, Nat.Commun. 2023, 14, 5881.[20] M. Shimasaki, T. Nishihara, N. Wada, Z. Liu, K. Matsuda, Y. Miyata,Y. Miyauchi, Appl. Phys. Express 2023, 16, 012010.[21] S. Ambardar, R. Kamh, Z. H. Withers, P. K. Sahoo, D. V. Voronine,Nanoscale 2022, 14, 8050.[22] M. Khan, M. N. Tripathi, A. Tripathi, Mater. Sci. Semicond. Process.2024, 177, 108339.[23] Y. Zhou, G. Scuri, D. S. Wild, A. A. High, A. Dibos, L. A. Jauregui, C.Shu, K. De Greve, K. Pistunova, A. Y. Joe, et al., Nat. Nanotechnol.2017, 12, 856.[24] G. Wang, C. Robert, M. M. Glazov, F. Cadiz, E. Courtade, T. Amand,D. Lagarde, T. Taniguchi, K. Watanabe, B. Urbaszek, et al., Phys. Rev.Lett. 2017, 119, 047401.[25] J.-M. Poumirol, I. Paradisanos, S. Shree, G. Agez, X. Marie, C. Robert,N. Mallet, P. R. Wiecha, G. Larrieu, V. Larrey, et al., ACS photonics2020, 7, 3106.[26] R. Rosati, I. Paradisanos, L. Huang, Z. Gan, A. George, K. Watanabe,T. Taniguchi, L. Lombez, P. Renucci, A. Turchanin, et al., Nat. Com-mun. 2023, 14, 2438.[27] J. Zipfel, M. Kulig, R. Perea-Causín, S. Brem, J. D. Ziegler, R. Rosati,T. Taniguchi, K. Watanabe, M. M. Glazov, E. Malic, et al., Phys. Rev. B2020, 101, 115430.[28] R. Perea-Causin, S. Brem, R. Rosati, R. Jago, M. Kulig, J. D. Ziegler, J.Zipfel, A. Chernikov, E. Malic, Nano Lett. 2019, 19, 7317.Adv. Optical Mater. 2025, 13, 2403009 2403009 (10 of 10) © 2024 The Author(s). Advanced Optical Materials published by Wiley-VCH GmbH 21951071, 2025, 10, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.202403009 by National Institute For, Wiley Online Library on [01/12/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advopticalmat.de Exciton Collimation, Focusing and Trapping Using Complex Transition Metal Dichalcogenide Lateral Heterojunctions 1. Introduction 2. Results 2.1. 80µ-PL Study of MoSe2-WSe2 LH 2.2. Statistical Approach of Exciton Diffusion 3. Discussion 3.1. One Interface: Exciton Distribution and Flux 3.2. Two Interfaces: Collimation and Focusing 3.3. Three Interfaces: Exciton Funneling and Trapping 4. Conclusion Supporting Information Acknowledgements Conflict of Interest Data Availability Statement Keywords