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@ARTICLE{Theilen:1048820,
      author       = {Theilen, Marcel and Kaidisch, Siegfried and Stettner, Monja
                      and Zajusch, Sarah and Fackelman, Eric and Adamkiewicz,
                      Alexa and Wallauer, Robert and Windischbacher, Andreas and
                      Kern, Christian S. and Ramsey, Michael G. and Bocquet,
                      François C. and Soubatch, Serguei and Tautz, F. Stefan and
                      Höfer, Ulrich and Puschnig, Peter},
      title        = {{O}bserving the spatial and temporal evolution of exciton
                      wave functions},
      journal      = {arXiv:2511.23001 [cond-mat.mtrl-sci]},
      publisher    = {arXiv},
      reportid     = {FZJ-2025-04928},
      year         = {2025},
      abstract     = {Excitons, the correlated electron-hole pairs governing
                      optical and transport properties in organic semiconductors,
                      have long resisted direct experimental access to their full
                      quantum-mechanical wave functions. Here, we use femtosecond
                      time-resolved photoemission orbital tomography (trPOT),
                      combining high-harmonic probe pulses with time- and
                      momentum-resolved photoelectron spectroscopy, to directly
                      image the momentum-space distribution and ultrafast dynamics
                      of excitons in $α$-sexithiophene thin films. We introduce a
                      quantitative model that enables reconstruction of the
                      exciton wave function in real space, including both its
                      spatial extent and its internal phase structure. The
                      reconstructed wave function reveals coherent delocalization
                      across approximately three molecular units and exhibits a
                      characteristic phase modulation, consistent with ab initio
                      calculations within the framework of many-body perturbation
                      theory. Time-resolved measurements further show a $\sim
                      20$\\% contraction of the exciton radius within 400 fs,
                      providing direct evidence of self-trapping driven by
                      exciton-phonon coupling. These results establish trPOT as a
                      general and experimentally accessible approach for resolving
                      exciton wave functions -- with spatial, phase, and temporal
                      sensitivity -- in a broad class of molecular and
                      low-dimensional materials.},
      keywords     = {Materials Science (cond-mat.mtrl-sci) (Other) / FOS:
                      Physical sciences (Other)},
      cin          = {PGI-3},
      cid          = {I:(DE-Juel1)PGI-3-20110106},
      pnm          = {5213 - Quantum Nanoscience (POF4-521) / Orbital Cinema -
                      Photoemission Orbital Cinematography: An ultrafast wave
                      function lab (101071259)},
      pid          = {G:(DE-HGF)POF4-5213 / G:(EU-Grant)101071259},
      typ          = {PUB:(DE-HGF)25},
      doi          = {10.48550/arXiv.2511.23001},
      url          = {https://juser.fz-juelich.de/record/1048820},
}