CRC/TRR227 Ultrafast Spin Dynamics
Published December 30, 2020 | Version 1.0
Journal article Open

Direct measurement of key exciton properties: energy, dynamics and spatial distribution of the wave function

Creators

  • 1. Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
  • 2. Laboratoire de Spectroscopie Ultrarapide and Lausanne Centre for Ultrafast Science (LACUS), École polytechnique fédérale de Lausanne, ISIC, Station 6, CH-1015 Lausanne, Switzerland
  • 3. Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik,Technische Universität Berlin, 10623 Berlin, Germany
  • 4. Max Planck Institute for the Structure and Dynamics of Matter and Center for Free Electron Laser Science, Luruper Chaussee 149, 22761 Hamburg, Germany
  • 5. Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, CH-1700 Fribourg, Switzerland
  • 6. SwissFEL, Paul Scherrer Institute, Villigen, Switzerland
  • 7. Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden

Description

Excitons, Coulomb-bound electron-hole pairs, are the fundamental excitations governing the optoelectronic properties of semiconductors. While optical signatures of excitons have been studied extensively, experimental access to the excitonic wave function itself has been elusive. Using multidimensional photoemission spectroscopy, we present a momentum-, energy- and time-resolved perspective on excitons in the layered semiconductor WSe2.  By tuning the excitation wavelength, we determine the energy-momentum signature of bright exciton formation and its difference from conventional single-particle excited states. The multidimensional data allows to retrieve fundamental exciton properties like the binding energy and the exciton-lattice coupling and to reconstruct the real-space excitonic distribution function via Fourier transform. All quantities are in excellent agreement with microscopic calculations. Our approach provides a full characterization of the exciton properties and is applicable to bright and dark excitons in semiconducting materials, heterostructures and devices. The data we uploaded here is the four-dimensional trARPES data used in this paper. 

Notes

This work was funded by the Max Planck Society, the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation and the H2020-EU.1.2.1. FET Open programs (Grant Nos. ERC-2015-CoG-682843, ERC-2015-AdG-694097, and OPTOlogic 899794), the Max Planck Society's Research Network BiGmax on Big-Data-Driven Materials-Science, and the German Research Foundation (DFG) within the Emmy Noether program (Grant No. RE 3977/1), through SFB 951 "Hybrid Inorganic/Organic Systems for Opto-Electronics (HIOS)" (Project No. 182087777, projects B12 and B17), the SFB/TRR 227 "Ultrafast Spin Dynamics" (projects A09 and B07), the Research Unit FOR 1700 "Atomic Wires" (project E5), and the Priority Program SPP 2244 (project 443366970). D.C.thanks the graduate school Advanced Materials (SFB 951) for support. S.B. acknowledges financial support from the NSERC-Banting Postdoctoral Fellowships Program. T.P. acknowledges financial support from the Alexander von Humboldt Foundation.

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Preprint: arXiv:2012.15328 (arXiv)