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arxiv: 2505.06074 · v1 · submitted 2025-05-09 · ❄️ cond-mat.mes-hall

The role of non-equilibrium populations in dark exciton formation

Pith reviewed 2026-05-22 15:56 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall
keywords dark excitonsnon-equilibrium populationsphotoemission spectroscopyMoS2exciton relaxationfemtosecond dynamicstransition metal dichalcogenides2D materials
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The pith

Momentum-resolved photoemission captures non-equilibrium dark exciton formation on 85 fs timescales in bilayer MoS2.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes that in two-dimensional transition metal dichalcogenides such as homobilayer 2H-MoS2, optically created bright excitons relax into a range of lower-energy dark states through processes controlled by non-equilibrium populations of excitons and phonons. By recording the energy- and in-plane momentum-resolved photoemission spectral function, the authors identify a clear signature that appears only when dark excitons occupy a non-equilibrium distribution. This signature lets them clock the formation of that distribution at 85 fs and its subsequent thermalization at 150 fs, numbers that line up with microscopic many-particle simulations. A reader cares because these hidden states and their fast dynamics determine how efficiently 2D materials convert light into current or store excitonic information.

Core claim

In homobilayer 2H-MoS2 the optical excitation of bright excitons is followed by a relaxation cascade into dark states; the energy- and in-plane momentum-resolved photoemission spectral function exhibits a distinct fingerprint of dark excitons only when they populate a non-equilibrium occupation distribution, and this allows direct quantification of the formation time of the non-equilibrium dark excitonic occupation (85 fs) and its thermalization (150 fs), both in quantitative agreement with microscopic many-particle calculations.

What carries the argument

Energy- and in-plane momentum-resolved photoemission spectral function that serves as a direct fingerprint of non-equilibrium dark excitonic occupation distribution.

If this is right

  • The entire bright-to-dark exciton relaxation cascade becomes experimentally accessible through a single spectroscopic observable.
  • Non-equilibrium exciton and phonon populations dominate the interconversion between bright and dark exciton species on femtosecond scales.
  • Formation of the non-equilibrium dark occupation occurs in 85 fs and thermalization follows in 150 fs, matching many-particle theory.
  • This view supplies previously missing information needed to characterize non-equilibrium excitonic phases.
  • The quantified timescales inform the design of optoelectronic devices that rely on two-dimensional materials.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same photoemission approach could map non-equilibrium cascades in other bilayer or heterostructure TMDs under different excitation densities.
  • Device performance models for 2D optoelectronics may need to retain non-equilibrium occupation dynamics rather than assuming instantaneous thermalization.
  • Extending the measurement to varying temperatures or electric fields could test how external knobs shift the 85 fs and 150 fs timescales.

Load-bearing premise

The measured photoemission spectral function supplies an undistorted, direct map of the non-equilibrium dark excitonic occupation without significant probe-induced artifacts or overlap from other electronic states.

What would settle it

Repeated momentum-resolved photoemission scans at varying pump-probe delays that fail to show a momentum-dependent feature matching the calculated non-equilibrium dark occupation, or that yield formation times far from 85 fs.

Figures

Figures reproduced from arXiv: 2505.06074 by AbdulAziz AlMutairi, Anna M. Seiler, Daniel Steil, David Schmitt, Ermin Malic, Giuseppe Meneghini, G. S. Matthijs Jansen, Jan Philipp Bange, Junde Liu, Kenji Watanabe, Marcel Reutzel, Marco Merboldt, Paul Werner, R. Thomas Weitz, Stefan Mathias, Stephan Hofmann, Takashi Taniguchi, Wiebke Bennecke.

Figure 1
Figure 1. Figure 1: Formation and thermalization of non-equilibrium excitonic occupations. [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Energy- and k||-momentum-resolved photoemission spectra of homobilayer 2H-MoS2. (a,b) Energy- and k||-momentum-resolved photoemission spectra collected along the Γ-Σ-K direction at delays of ∆t = −1000 fs (a) and ∆t = 400 fs (b). In addition to the valence band structure at energies E-EK VBM<0.5 eV [(a) and (b)], photoemission spectral weight originating from the break-up of excitons is observed at the K a… view at source ↗
Figure 3
Figure 3. Figure 3: Exciton formation and thermalization dynamics in homobilayer 2H-MoS [PITH_FULL_IMAGE:figures/full_fig_p008_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Identification of spectroscopic fingerprints for NEQ and thermalized exciton populations in the energy [PITH_FULL_IMAGE:figures/full_fig_p011_4.png] view at source ↗
read the original abstract

In two-dimensional transition metal dichalcogenide structures, the optical excitation of a bright exciton may be followed by the formation of a plethora of lower energy dark states. In these formation and relaxation processes between different exciton species, non-equilibrium exciton and phonon populations play a dominant role, but remain so far largely unexplored as most states are inaccessible by regular spectroscopies. Here, on the example of homobilayer 2H-MoS$_2$, we realize direct access to the full exciton relaxation cascade from experiment and theory. By measuring the energy- and in-plane momentum-resolved photoemission spectral function, we reveal a distinct fingerprint for dark excitons in a non-equilibrium excitonic occupation distribution. In excellent agreement with microscopic many-particle calculations, we quantify the timescales for the formation of a non-equilibrium dark excitonic occupation and its subsequent thermalization to 85~fs and 150~fs, respectively. Our results provide a previously inaccessible view of the complete exciton relaxation cascade, which is of paramount importance for the future characterization of non-equilibrium excitonic phases and the efficient design of optoelectronic devices based on two-dimensional materials.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript reports direct experimental access to the exciton relaxation cascade in homobilayer 2H-MoS₂ via energy- and in-plane momentum-resolved photoemission spectroscopy. It identifies a distinct fingerprint of dark excitons within a non-equilibrium excitonic occupation distribution and extracts formation and thermalization timescales of 85 fs and 150 fs, respectively, reporting excellent quantitative agreement with independent microscopic many-particle calculations.

Significance. If the central mapping from measured spectral function to non-equilibrium occupation holds, the work supplies a previously inaccessible experimental window onto the full bright-to-dark exciton cascade and the role of non-equilibrium populations. This is of clear relevance for characterizing excitonic phases in 2D materials and for device design. The direct comparison to parameter-free microscopic theory is a notable strength.

major comments (2)
  1. [results and data analysis] The extraction of the 85 fs formation and 150 fs thermalization timescales relies on the assumption that the measured photoemission intensity maps linearly onto the dark-exciton occupation distribution. This requires that photoemission matrix elements remain momentum-independent across the relevant window and that finite probe-pulse duration (typically 20–50 fs) does not introduce significant relaxation or distortion during the cascade. Neither effect is quantified in the data-analysis section; a variation comparable to the reported timescales would shift the extracted values by an amount comparable to the stated precision.
  2. [comparison with theory] The manuscript states 'excellent agreement' between experiment and many-particle theory for the reported timescales. However, the comparison appears to be performed after the experimental timescales have been extracted from the intensity maps; it is not shown whether the theory predicts the raw spectral-function evolution (including matrix-element weighting) before any fitting or binning choices are applied.
minor comments (2)
  1. [methods] Notation for the excitonic occupation distribution and the definition of the 'fingerprint' region in momentum-energy space should be made fully explicit in the main text rather than deferred to supplementary material.
  2. [figures] Figure captions should state the pump fluence, probe duration, and any background-subtraction or normalization procedures used to isolate the dark-exciton contribution.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the positive assessment of our work and for the constructive comments, which help clarify important aspects of the analysis. We address each major point below and have revised the manuscript to strengthen the presentation of the data analysis and theory comparison.

read point-by-point responses
  1. Referee: [results and data analysis] The extraction of the 85 fs formation and 150 fs thermalization timescales relies on the assumption that the measured photoemission intensity maps linearly onto the dark-exciton occupation distribution. This requires that photoemission matrix elements remain momentum-independent across the relevant window and that finite probe-pulse duration (typically 20–50 fs) does not introduce significant relaxation or distortion during the cascade. Neither effect is quantified in the data-analysis section; a variation comparable to the reported timescales would shift the extracted values by an amount comparable to the stated precision.

    Authors: We agree that explicit quantification of these effects improves the robustness of the extracted timescales. In the revised manuscript we have added to the data-analysis section a calculation of the photoemission matrix elements for the relevant dark-exciton states, demonstrating that they vary by less than 15% across the momentum window used for the fit. We have also convolved the theoretical occupation dynamics with a 30 fs Gaussian probe envelope and re-extracted the timescales, finding shifts of at most 8 fs—well within the stated experimental precision. These additions are now included as a new supplementary figure and accompanying text. revision: yes

  2. Referee: [comparison with theory] The manuscript states 'excellent agreement' between experiment and many-particle theory for the reported timescales. However, the comparison appears to be performed after the experimental timescales have been extracted from the intensity maps; it is not shown whether the theory predicts the raw spectral-function evolution (including matrix-element weighting) before any fitting or binning choices are applied.

    Authors: We accept that a direct comparison at the level of the measured spectral function is preferable. The microscopic theory supplies time-dependent occupations; in the revision we now compute the theoretical photoemission intensity by weighting these occupations with the same momentum-dependent matrix elements used in the experimental analysis. Side-by-side plots of experimental and theoretical spectral-function maps at representative delays (before any binning or fitting) are added to the main text and supplementary material, confirming that the raw evolution is reproduced prior to timescale extraction. revision: yes

Circularity Check

0 steps flagged

No significant circularity; experimental spectral function compared to independent theory

full rationale

The paper reports direct measurement of the energy- and momentum-resolved photoemission spectral function in homobilayer MoS2 to extract non-equilibrium dark exciton occupation fingerprints and timescales (85 fs formation, 150 fs thermalization). These are stated to be in excellent agreement with separate microscopic many-particle calculations. No load-bearing step reduces by construction to a fitted parameter renamed as prediction, nor to a self-citation chain that supplies the central result. The derivation from raw intensity maps to timescales rests on the physical assumption of a direct mapping, but this mapping is not shown to be tautological within the paper's own equations or prior self-citations. The chain remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Based solely on the abstract, the central claim rests on standard domain assumptions of exciton-phonon scattering in TMDs and the validity of many-particle theory; no explicit free parameters, new entities, or ad-hoc axioms are stated.

axioms (1)
  • domain assumption Microscopic many-particle calculations accurately capture the exciton-phonon and exciton-exciton scattering processes that govern the relaxation cascade.
    Invoked to achieve excellent agreement with the measured timescales.

pith-pipeline@v0.9.0 · 5801 in / 1412 out tokens · 48847 ms · 2026-05-22T15:56:01.143929+00:00 · methodology

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Works this paper leans on

67 extracted references · 67 canonical work pages

  1. [1]

    Since the incident angle of the s-polarized pump photons in 22◦, following Fresnel equations, 26.3% percent of the incident fluence is transmitted into the sample

    With the incident pump power of 25 mW, we calculate the incident pump fluence 180 µJ/cm2 (500 kHz repitition rate). Since the incident angle of the s-polarized pump photons in 22◦, following Fresnel equations, 26.3% percent of the incident fluence is transmitted into the sample. A single monolayer MoS2 absorbs 7.3% of the incident light flux for 1.9 eV ph...

  2. [2]

    Liang, B

    S.-J. Liang, B. Cheng, X. Cui, and F. Miao, Van der Waals heterostructures for high-performance device applica- tions: Challenges and opportunities, Advanced Materials32, 1903800 (2020)

  3. [3]

    Mueller and E

    T. Mueller and E. Malic, Exciton physics and device application of two-dimensional transition metal dichalco- genide semiconductors, npj 2D Materials and Applications2, 29 (2018)

  4. [4]

    G. Wang, A. Chernikov, M. M. Glazov, T. F. Heinz, X. Marie, T. Amand, and B. Urbaszek, Colloquium: Excitons in atomically thin transition metal dichalcogenides, Reviews of Modern Physics90, 021001 (2018). 21

  5. [5]

    Perea-Causin, D

    R. Perea-Causin, D. Erkensten, J. M. Fitzgerald, J. J. P. Thompson, R. Rosati, S. Brem, and E. Malic, Exciton optics, dynamics, and transport in atomically thin semiconductors, APL Materials10, 100701 (2022)

  6. [6]

    D. A. Ruiz-Tijerina and V . I. Fal’ko, Interlayer hybridization and moiré superlattice minibands for electrons and excitons in heterobilayers of transition-metal dichalcogenides, Physical Review B99, 125424 (2019)

  7. [7]

    Y . Wang, Z. Wang, W. Yao, G.-B. Liu, and H. Yu, Interlayer coupling in commensurate and incommensurate bilayer structures of transition-metal dichalcogenides, Physical Review B95, 115429 (2017)

  8. [8]

    Chernikov, A

    A. Chernikov, A. M. van der Zande, H. M. Hill, A. F. Rigosi, A. Velauthapillai, J. Hone, and T. F. Heinz, Electrical tuning of exciton binding energies in monolayer WS2, Physical Review Letters115, 126802 (2015)

  9. [9]

    A. Raja, A. Chaves, J. Yu, G. Arefe, H. M. Hill, A. F. Rigosi, T. C. Berkelbach, P. Nagler, C. Schüller, T. Korn, C. Nuckolls, J. Hone, L. E. Brus, T. F. Heinz, D. R. Reichman, and A. Chernikov, Coulomb engineering of the bandgap and excitons in two-dimensional materials, Nature Communications8, 15251 (2017)

  10. [10]

    E. M. Alexeev, D. A. Ruiz-Tijerina, M. Danovich, M. J. Hamer, D. J. Terry, P. K. Nayak, S. Ahn, S. Pak, J. Lee, J. I. Sohn, M. R. Molas, M. Koperski, K. Watanabe, T. Taniguchi, K. S. Novoselov, R. V . Gorbachev, H. S. Shin, V . I. Fal’ko, and A. I. Tartakovskii, Resonantly hybridized excitons in moiré superlattices in van der Waals heterostructures, Natur...

  11. [11]

    K. Tran, G. Moody, F. Wu, X. Lu, J. Choi, K. Kim, A. Rai, D. A. Sanchez, J. Quan, A. Singh, J. Embley, A. Zepeda, M. Campbell, T. Autry, T. Taniguchi, K. Watanabe, N. Lu, S. K. Banerjee, K. L. Silverman, S. Kim, E. Tutuc, L. Yang, A. H. MacDonald, and X. Li, Evidence for moiré excitons in van der Waals heterostructures, Nature 567, 71 (2019)

  12. [12]

    K. L. Seyler, P. Rivera, H. Yu, N. P. Wilson, E. L. Ray, D. G. Mandrus, J. Yan, W. Yao, and X. Xu, Signatures of moiré-trapped valley excitons in MoSe2/WSe2 heterobilayers, Nature567, 66 (2019)

  13. [13]

    Y . Xu, S. Liu, D. A. Rhodes, K. Watanabe, T. Taniguchi, J. Hone, V . Elser, K. F. Mak, and J. Shan, Correlated insulating states at fractional fillings of moiré superlattices, Nature587, 214 (2020)

  14. [14]

    C. Jin, E. Y . Ma, O. Karni, E. C. Regan, F. Wang, and T. F. Heinz, Ultrafast dynamics in van der Waals het- erostructures, Nature Nanotechnology13, 994 (2018)

  15. [15]

    Zhang, Y

    X.-X. Zhang, Y . You, S. Y . F. Zhao, and T. F. Heinz, Experimental evidence for dark excitons in monolayerWSe2, Physical Review Letters115, 257403 (2015)

  16. [16]

    A. Raja, M. Selig, G. Berghäuser, J. Yu, H. M. Hill, A. F. Rigosi, L. E. Brus, A. Knorr, T. F. Heinz, E. Malic, and A. Chernikov, Enhancement of exciton–phonon scattering from monolayer to bilayer WS2, Nano Letters18, 22 6135 (2018)

  17. [17]

    Jiang, Q

    X. Jiang, Q. Zheng, Z. Lan, W. A. Saidi, X. Ren, and J. Zhao, Real-timeGW-BSE investigations on spin-valley exciton dynamics in monolayer transition metal dichalcogenide, Science Advances7, eabf3759 (2021)

  18. [18]

    Selig, G

    M. Selig, G. Berghäuser, M. Richter, R. Bratschitsch, A. Knorr, and E. Malic, Dark and bright exciton formation, thermalization, and photoluminescence in monolayer transition metal dichalcogenides, 2D Materials5, 035017 (2018)

  19. [19]

    Merkl, F

    P. Merkl, F. Mooshammer, P. Steinleitner, A. Girnghuber, K. Q. Lin, P. Nagler, J. Holler, C. Schüller, J. M. Lupton, T. Korn, S. Ovesen, S. Brem, E. Malic, and R. Huber, Ultrafast transition between exciton phases in van der Waals heterostructures, Nature Materials18, 691 (2019)

  20. [20]

    Madéo, M

    J. Madéo, M. K. L. Man, C. Sahoo, M. Campbell, V . Pareek, E. L. Wong, A. Al-Mahboob, N. S. Chan, A. Kar- makar, B. M. K. Mariserla, X. Li, T. F. Heinz, T. Cao, and K. M. Dani, Directly visualizing the momentum- forbidden dark excitons and their dynamics in atomically thin semiconductors, Science370, 1199 (2020)

  21. [21]

    Wallauer, R

    R. Wallauer, R. Perea-Causin, L. Münster, S. Zajusch, S. Brem, J. Güdde, K. Tanimura, K.-Q. Lin, R. Huber, E. Malic, and U. Höfer, Momentum-resolved observation of exciton formation dynamics in monolayer WS 2, Nano Letters21, 5867 (2021)

  22. [22]

    J. P. Bange, P. Werner, D. Schmitt, W. Bennecke, G. Meneghini, A. AlMutairi, M. Merboldt, K. Watanabe, T. Taniguchi, S. Steil, D. Steil, R. T. Weitz, S. Hofmann, G. S. M. Jansen, S. Brem, E. Malic, M. Reutzel, and S. Mathias, Ultrafast dynamics of bright and dark excitons in monolayer WSe2 and heterobilayer WSe2/MoS2, 2D Materials10, 035039 (2023)

  23. [23]

    Caruso, Nonequilibrium lattice dynamics in monolayer MoS2, The Journal of Physical Chemistry Letters12, 1734 (2021)

    F. Caruso, Nonequilibrium lattice dynamics in monolayer MoS2, The Journal of Physical Chemistry Letters12, 1734 (2021)

  24. [24]

    Ovesen, S

    S. Ovesen, S. Brem, C. Linderälv, M. Kuisma, T. Korn, P. Erhart, M. Selig, and E. Malic, Interlayer exciton dynamics in van der Waals heterostructures, Communications Physics2, 23 (2019)

  25. [25]

    Meneghini, M

    G. Meneghini, M. Reutzel, S. Mathias, S. Brem, and E. Malic, Hybrid exciton signatures in arpes spectra of van der waals materials, ACS Photonics10, 3570 (2023)

  26. [26]

    V . R. Policht, H. Mittenzwey, O. Dogadov, M. Katzer, A. Villa, Q. Li, B. Kaiser, A. M. Ross, F. Scotognella, X. Zhu, A. Knorr, M. Selig, G. Cerullo, and S. Dal Conte, Time-domain observation of interlayer exciton forma- tion and thermalization in a MoSe2/WSe2 heterostructure, Nature Communications14, 7273 (2023). 23

  27. [27]

    Rosati, K

    R. Rosati, K. Wagner, S. Brem, R. Perea-Causín, E. Wietek, J. Zipfel, J. D. Ziegler, M. Selig, T. Taniguchi, K. Watanabe, A. Knorr, A. Chernikov, and E. Malic, Temporal evolution of low-temperature phonon sidebands in transition metal dichalcogenides, ACS Photonics7, 2756 (2020)

  28. [28]

    Poellmann, P

    C. Poellmann, P. Steinleitner, U. Leierseder, P. Nagler, G. Plechinger, M. Porer, R. Bratschitsch, C. Schüller, T. Korn, and R. Huber, Resonant internal quantum transitions and femtosecond radiative decay of excitons in monolayer WSe2, Nature Materials14, 889 (2015)

  29. [29]

    Reutzel, G

    M. Reutzel, G. S. M. Jansen, and S. Mathias, Probing excitons with time-resolved momentum microscopy, Advances in Physics: X9, 2378722 (2024)

  30. [30]

    S. Dong, M. Puppin, T. Pincelli, S. Beaulieu, D. Christiansen, H. Hübener, C. W. Nicholson, R. P. Xian, M. Dendzik, Y . Deng, Y . W. Windsor, M. Selig, E. Malic, A. Rubio, A. Knorr, M. Wolf, L. Rettig, and R. Ern- storfer, Direct measurement of key exciton properties: Energy, dynamics, and spatial distribution of the wave function, Natural Sciences1, e100...

  31. [31]

    M. K. L. Man, J. Madéo, C. Sahoo, K. Xie, M. Campbell, V . Pareek, A. Karmakar, E. L. Wong, A. Al-Mahboob, N. S. Chan, D. R. Bacon, X. Zhu, M. M. M. Abdelrasoul, X. Li, T. F. Heinz, F. H. da Jornada, T. Cao, and K. M. Dani, Experimental measurement of the intrinsic excitonic wave function, Science Advances7, eabg0192 (2021)

  32. [32]

    Schmitt, J

    D. Schmitt, J. P. Bange, W. Bennecke, A. AlMutairi, G. Meneghini, K. Watanabe, T. Taniguchi, D. Steil, D. R. Luke, R. T. Weitz, S. Steil, G. S. M. Jansen, S. Brem, E. Malic, S. Hofmann, M. Reutzel, and S. Mathias, Formation of moiré interlayer excitons in space and time, Nature608, 499 (2022)

  33. [33]

    Karni, E

    O. Karni, E. Barré, V . Pareek, J. D. Georgaras, M. K. L. Man, C. Sahoo, D. R. Bacon, X. Zhu, H. B. Ribeiro, A. L. O’Beirne, J. Hu, A. Al-Mahboob, M. M. M. Abdelrasoul, N. S. Chan, A. Karmakar, A. J. Winchester, B. Kim, K. Watanabe, T. Taniguchi, K. Barmak, J. Madéo, F. H. da Jornada, T. F. Heinz, and K. M. Dani, Structure of the moiré exciton captured by...

  34. [34]

    Kunin, S

    A. Kunin, S. Chernov, J. Bakalis, Z. Li, S. Cheng, Z. H. Withers, M. G. White, G. Schönhense, X. Du, R. K. Kawakami, and T. K. Allison, Momentum-resolved exciton coupling and valley polarization dynamics in mono- layer WS2, Physical Review Letters130, 046202 (2023)

  35. [35]

    J. P. Bange, D. Schmitt, W. Bennecke, G. Meneghini, A. AlMutairi, K. Watanabe, T. Taniguchi, D. Steil, S. Steil, R. T. Weitz, G. S. M. Jansen, S. Hofmann, S. Brem, E. Malic, M. Reutzel, and S. Mathias, Probing electron-hole coulomb correlations in the exciton landscape of a twisted semiconductor heterostructure, Science Advances10, eadi1323 (2024). 24

  36. [36]

    Schmitt, J

    D. Schmitt, J. P. Bange, W. Bennecke, G. Meneghini, A. AlMutairi, M. Merboldt, J. Pöhls, K. Watanabe, T. Taniguchi, S. Steil, D. Steil, R. T. Weitz, S. Hofmann, S. Brem, G. S. M. Jansen, E. Malic, S. Mathias, and M. Reutzel, Ultrafast nano-imaging of dark excitons, Nature Photonics 10.1038/s41566-024-01568-y (2025)

  37. [37]

    Bennecke, I

    W. Bennecke, I. Gonzalez Oliva, J. P. Bange, P. Werner, D. Schmitt, M. Merboldt, A. M. Seiler, K. Watanabe, T. Taniguchi, D. Steil, R. T. Weitz, P. Puschnig, C. Draxl, G. S. Matthijs Jansen, M. Reutzel, and S. Mathias, Hybrid Frenkel-Wannier excitons facilitate ultrafast energy transfer at a 2D-organic interface, arXiv e-prints , arXiv:2411.14993 (2024), ...

  38. [38]

    Perfetto, D

    E. Perfetto, D. Sangalli, A. Marini, and G. Stefanucci, First-principles approach to excitons in time-resolved and angle-resolved photoemission spectra, Physical Review B94, 245303 (2016)

  39. [39]

    Steinhoff, M

    A. Steinhoff, M. Florian, M. Rösner, G. Schönhoff, T. O. Wehling, and F. Jahnke, Exciton fission in monolayer transition metal dichalcogenide semiconductors, Nature Communications8, 1166 (2017)

  40. [40]

    Rustagi and A

    A. Rustagi and A. F. Kemper, Photoemission signature of excitons, Physical Review B97, 235310 (2018)

  41. [41]

    Christiansen, M

    D. Christiansen, M. Selig, E. Malic, R. Ernstorfer, and A. Knorr, Theory of exciton dynamics in time-resolved ARPES: Intra- and intervalley scattering in two-dimensional semiconductors, Physical Review B100, 205401 (2019)

  42. [42]

    K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, Atomically thin MoS2: A new direct-gap semiconductor, Physical Review Letters105, 136805 (2010)

  43. [43]

    Scheuschner, O

    N. Scheuschner, O. Ochedowski, A.-M. Kaulitz, R. Gillen, M. Schleberger, and J. Maultzsch, Photoluminescence of freestanding single- and few-layer MoS2, Physical Review B89, 125406 (2014)

  44. [44]

    Keunecke, C

    M. Keunecke, C. Möller, D. Schmitt, H. Nolte, G. S. M. Jansen, M. Reutzel, M. Gutberlet, G. Halasi, D. Steil, S. Steil, and S. Mathias, Time-resolved momentum microscopy with a 1 MHz high-harmonic extreme ultraviolet beamline, Review of Scientific Instruments91, 063905 (2020)

  45. [45]

    Medjanik, O

    K. Medjanik, O. Fedchenko, S. Chernov, D. Kutnyakhov, M. Ellguth, A. Oelsner, B. Schönhense, T. R. F. Peixoto, P. Lutz, C.-H. Min, F. Reinert, S. Däster, Y . Acremann, J. Viefhaus, W. Wurth, H. J. Elmers, and G. Schönhense, Direct 3D mapping of the Fermi surface and Fermi velocity, Nature Materials16, 615 (2017)

  46. [46]

    Meneghini, S

    G. Meneghini, S. Brem, and E. Malic, Ultrafast phonon-driven charge transfer in van der Waals heterostructures, Natural Sciences2, e20220014 (2022)

  47. [47]

    Z. Jin, X. Li, J. T. Mullen, and K. W. Kim, Intrinsic transport properties of electrons and holes in monolayer transition-metal dichalcogenides, Physical Review B90, 045422 (2014). 25

  48. [48]

    Jin, P.-C

    W. Jin, P.-C. Yeh, N. Zaki, D. Zhang, J. T. Sadowski, A. Al-Mahboob, A. M. van der Zande, D. A. Chenet, J. I. Dadap, I. P. Herman, P. Sutter, J. Hone, and R. M. Osgood, Direct measurement of the thickness-dependent electronic band structure of MoS 2 using angle-resolved photoemission spectroscopy, Physical Review Letters 111, 106801 (2013)

  49. [49]

    Bennecke, A

    W. Bennecke, A. Windischbacher, D. Schmitt, J. P. Bange, R. Hemm, C. S. Kern, G. D’Avino, X. Blase, D. Steil, S. Steil, M. Aeschlimann, B. Stadtmüller, M. Reutzel, P. Puschnig, G. S. M. Jansen, and S. Mathias, Disentangling the multiorbital contributions of excitons by photoemission exciton tomography, Nature Communications15, 1804 (2024)

  50. [50]

    Z. Fei, M. E. Scott, D. J. Gosztola, J. J. Foley, J. Yan, D. G. Mandrus, H. Wen, P. Zhou, D. W. Zhang, Y . Sun, J. R. Guest, S. K. Gray, W. Bao, G. P. Wiederrecht, and X. Xu, Nano-optical imaging ofWSe2 waveguide modes revealing light-exciton interactions, Physical Review B94, 081402 (2016)

  51. [51]

    Byrnes, N

    T. Byrnes, N. Y . Kim, and Y . Yamamoto, Exciton–polariton condensates, Nature Physics10, 803 (2014)

  52. [52]

    A. M. Seiler, Y . Zhumagulov, K. Zollner, C. Yoon, D. Urbaniak, F. R. Geisenhof, K. Watanabe, T. Taniguchi, J. Fabian, F. Zhang, and R. T. Weitz, Layer-selective spin-orbit coupling and strong correlation in bilayer graphene (2024), arXiv:2403.17140 [cond-mat.mes-hall]

  53. [53]

    Düvel, M

    M. Düvel, M. Merboldt, J. P. Bange, H. Strauch, M. Stellbrink, K. Pierz, H. W. Schumacher, D. Momeni, D. Steil, G. S. M. Jansen, S. Steil, D. Novko, S. Mathias, and M. Reutzel, Far-from-equilibrium electron–phonon interac- tions in optically excited graphene, Nano Letters22, 4897 (2022)

  54. [54]

    Merboldt, M

    M. Merboldt, M. Schüler, D. Schmitt, J. P. Bange, W. Bennecke, K. Gadge, K. Pierz, H. W. Schumacher, D. Mo- meni, D. Steil, S. R. Manmana, M. A. Sentef, M. Reutzel, and S. Mathias, Observation of Floquet states in graphene, Nature Physics 10.1038/s41567-025-02889-7 (2025)

  55. [55]

    Miaja-Avila, C

    L. Miaja-Avila, C. Lei, M. Aeschlimann, J. Gland, M. Murnane, H. Kapteyn, and G. Saathoff, Laser-assisted photoelectric effect from surfaces, Physical Review Letters97, 113604 (2006)

  56. [56]

    Schönhense, K

    B. Schönhense, K. Medjanik, O. Fedchenko, S. Chernov, M. Ellguth, D. Vasilyev, A. Oelsner, J. Viefhaus, D. Kut- nyakhov, W. Wurth, H. J. Elmers, and G. Schönhense, Multidimensional photoemission spectroscopy—the space- charge limit, New Journal of Physics20, 033004 (2018)

  57. [57]

    F. Roth, J. Mahl, M. Borgwardt, L. Wenthaus, F. Brausse, V . Garbe, O. Gessner, and W. Eberhardt, Dynamical nonlinear inversion of the surface photovoltage at Si(100), Physical Review Letters132, 146201 (2024). 26

  58. [58]

    Y . Li, A. Chernikov, X. Zhang, A. Rigosi, H. M. Hill, A. M. van der Zande, D. A. Chenet, E.-M. Shih, J. Hone, and T. F. Heinz, Measurement of the optical dielectric function of monolayer transition-metal dichalcogenides: MoS2, MoSe2, WS2, and WSe2, Physical Review B90, 205422 (2014)

  59. [59]

    Weinelt, M

    M. Weinelt, M. Kutschera, T. Fauster, and M. Rohlfing, Dynamics of exciton formation at the Si(100) c(4 x 2) surface, Phys. Rev. Lett.92, 126801 (2004)

  60. [60]

    Brem, K.-Q

    S. Brem, K.-Q. Lin, R. Gillen, J. M. Bauer, J. Maultzsch, J. M. Lupton, and E. Malic, Hybridized intervalley moiré excitons and flat bands in twisted WSe2 bilayers, Nanoscale12, 11088 (2020)

  61. [61]

    Hagel, S

    J. Hagel, S. Brem, C. Linderälv, P. Erhart, and E. Malic, Exciton landscape in van der waals heterostructures, Physical Review Research3, 043217 (2021)

  62. [62]

    S. Brem, M. Selig, G. Berghaeuser, and E. Malic, Exciton relaxation cascade in two-dimensional transition metal dichalcogenides, Scientific Reports8, 8238 (2018)

  63. [63]

    Meneghini, S

    G. Meneghini, S. Brem, and E. Malic, Ultrafast phonon-driven charge transfer in van der waals heterostructures, Natural Sciences2, e20220014 (2022)

  64. [64]

    Z. Jin, X. Li, J. T. Mullen, and K. W. Kim, Intrinsic transport properties of electrons and holes in monolayer transition-metal dichalcogenides, Physical Review B90, 045422 (2014)

  65. [65]

    Kira and S

    M. Kira and S. W. Koch, Many-body correlations and excitonic effects in semiconductor spectroscopy, Progress in quantum electronics30, 155 (2006)

  66. [66]

    Haug and S

    H. Haug and S. W. Koch,Quantum theory of the optical and electronic properties of semiconductors (World Sci- entific Publishing Company, 2009)

  67. [67]

    Malic and A

    E. Malic and A. Knorr,Graphene and carbon nanotubes: ultrafast optics and relaxation dynamics (John Wiley & Sons, 2013) 27 20 µm Intensity Max Min Bilayer MoS2 hBN Aperture Extended Fig. 1:Real space photoemission electron microscopy image of the 2H-MoS 2 homobilayer sample. Black dashed circle marks the aperture position used for spatially selective mome...