Signatures of a degenerate many-body state of interlayer excitons in a van der Waals heterostack

Sigl, Lukas; Sigger, Florian; Kronowetter, Fabian; Kiemle, Jonas; Klein, Julian; Watanabe, Kenji; Taniguchi, Takashi; Finley, Jonathan J.; Wurstbauer, Ursula; Holleitner, Alexander W.

doi:10.1103/physrevresearch.2.042044

Cited by 63 publications

(55 citation statements)

References 46 publications

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“…In contrast, on the heterostack region of this first sample (I), intralayer exciton emission is quenched most likely due to an effective charge transfer between the layers [5,10]. Instead, we observe an emerging emission line around 1.4 eV (black), which is attributed to the formation of IXs with the electron residing in MoSe 2 and the hole in WSe 2 [14].…”

Section: Resultsmentioning

confidence: 66%

“…For increasing excitation powers, IX (2) and IX (3) emerge and finally dominate the photoluminescence, as reported by us before in ref. [14].…”

Section: Resultsmentioning

confidence: 99%

“…Such exciton ensembles are ideal to explore the many-body phase diagram in quasiequilibrium. Due to the bosonic nature of IXs in combination with a permanent out-of-plane electric dipole moment [10,11], a versatile interaction-driven phase diagram with classical and quantum phases, including superfluidity and a quasi condensation is expected [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

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Optical dipole orientation of interlayer excitons in MoSe$_{2}$-WSe$_{2}$ heterostacks

Sigl,

Troue,

Katzer

et al. 2021

Preprint

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We report on the far-field photoluminescence intensity distribution of interlayer excitons in MoSe2-WSe2 heterostacks as measured by back focal plane imaging in the temperature range between 1.7 K and 20 K. By comparing the data with an analytical model describing the dipolar emission pattern in a dielectric environment, we are able to obtain the relative contributions of the in-and out-of-plane transition dipole moments associated to the interlayer exciton photon emission. We determine the transition dipole moments for all observed interlayer exciton transitions to be (99 ± 1)% in-plane for R-and H-type stacking, independent of the excitation power and therefore the density of the exciton ensemble in the experimentally examined range. Finally, we discuss the limitations of the presented measurement technique to observe correlation effects in exciton ensembles.

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Section: Resultsmentioning

confidence: 66%

“…For increasing excitation powers, IX (2) and IX (3) emerge and finally dominate the photoluminescence, as reported by us before in ref. [14].…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical dipole orientation of interlayer excitons in MoSe$_{2}$-WSe$_{2}$ heterostacks

Sigl,

Troue,

Katzer

et al. 2021

Preprint

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“…IXs also carry the valley information and have applications in valleytronics [10,11]. The emergence of IXs promotes fundamental research of many-body interactions [12] and exciton condensation [13]. It also triggers applications in excitonic circuits and valleytronics.…”

Section: Introductionmentioning

confidence: 99%

Site-controlled interlayer coupling in WSe2/2D perovskite heterostructure

Wei

Wen

et al. 2022

Sci. China Mater.

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Interlayer excitons (IXs) formed in transition metal dichalcogenides (TMDs)/two-dimensional (2D) perovskite heterostructures are emerging as new platforms in the research of excitons. Compared with IXs in TMD van der Waals heterostructures, IXs can be robustly formed in TMDs/ 2D perovskite heterostructures regardless of the twist angle and thermal annealing process. Efficient control of interlayer coupling is essential for realizing their functionalities and enhancing their performances. Nevertheless, the study on the control of interlayer coupling strength between TMD and 2D perovskites is elusive. Therefore, we realize the control of interlayer coupling between monolayer WSe 2 and (iso-BA) 2 PbI 4 with SiO 2 pillars in situ. An abnormal 10-nm blue shift and 2.5 times photoluminescence intensity enhancement were observed for heterostructures on the pillar, which was contrary to the red shift observed in TMD heterobilayers. We attributed the abnormal blue shift to the enhanced interlayer coupling arising from the reduced gap between constituent layers. In addition, IXs became more dominant over intralayer excitons with enhanced coupling. The interlayer coupling could be further engineered by tuning the height (h) and diameter (d) of pillars. In particular, an additional triplet IX showed up for the pillar with an h/d ratio of 0.6 due to the symmetry breaking of monolayer WSe 2 . The symmetry breaking also induced an anisotropic response of IXs. Our study is beneficial for tuning and enhancing the performance of IX-based devices, exciton localization and quantum emitters.

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“…Indeed, in recent literature, exciton condensation has been observed—computationally and experimentally—in bilayer structures 22 , 24 as well as multilayer van der Waals heterostructures. 19 , 25 , 27 Moreover, recent theoretical results by Safaei and Mazziotti 24 show that exciton condensation can potentially occur in bilayers of nonextended molecules. For multilayer systems, the excitons can flow through the stack to transfer energy.…”

mentioning

confidence: 99%

Exciton Condensation in Molecular-Scale van der Waals Stacks

Schouten

Sager

Mazziotti

2021

J. Phys. Chem. Lett.

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Recent experiments have realized the Bose–Einstein condensation of excitons, known as exciton condensation, in extended systems such as bilayer graphene and van der Waals heterostructures. Here we computationally demonstrate the beginnings of exciton condensation in multilayer, molecular-scale van der Waals stacks composed of benzene subunits. The populations of excitons, which are computed from the largest eigenvalue of the particle-hole reduced density matrix (RDM) through advanced variational RDM calculations, are shown to increase with the length of the stack. The large eigenvalue indicates a nonclassical long-range ordering of the excitons that can support the frictionless flow of energy. Moreover, we use chemical substitutions and geometric modifications to tune the extent of the condensation. Results suggest exciton condensation in a potentially large family of molecular systems with applications to energy-efficient transport.

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Signatures of a degenerate many-body state of interlayer excitons in a van der Waals heterostack

Cited by 63 publications

References 46 publications

Optical dipole orientation of interlayer excitons in MoSe$_{2}$-WSe$_{2}$ heterostacks

Optical dipole orientation of interlayer excitons in MoSe$_{2}$-WSe$_{2}$ heterostacks

Site-controlled interlayer coupling in WSe2/2D perovskite heterostructure

Exciton Condensation in Molecular-Scale van der Waals Stacks

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