Regensburg 2019 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 21: Quantum Nanophotonics in Solid State Systems
HL 21.3: Vortrag
Dienstag, 2. April 2019, 14:30–14:45, H33
Giant Rydberg excitons in the presence of an ultralow-density electron-hole plasma — Julian Heckötter1, Martin Bergen1, Marcel Freitag1, Dietmar Fröhlich1, Manfred Bayer1, Peter Grünwald2, Florian Schöne2, Dirk Semkat3, Heinrich Stolz2, Stefan Scheel2, and •Marc Aßmann1 — 1Experimentelle Physik 2, TU Dortmund, 44221 Dortmund — 2Institut für Physik, Universität Rostock, Albert-Einstein-Straße 23-24, 18059 Rostock — 3Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, Felix-Hausdorff-Straße 6, 17489 Greifswald
Giant Rydberg excitons in Cu2O show a spatial extension up the micrometer range and huge interactions, which may result in intriguing blockade effects similar to the Rydberg blockade known from cold atom physics. We study the Rydberg exciton absorption spectrum in the presence of free carriers injected by above-bandgap illumination. Already at plasma densities below one hundredth electron-hole pair per µm3, exciton lines are bleached, starting from the highest observed principal quantum number, while their energies remain constant. Also, the band gap decreases due to correlation effects with the plasma. An exciton line loses oscillator strength when the band gap approaches its energy, vanishing completely at the crossing point. Adapting a plasma-physics approach, we describe the observations by an effective Bohr radius that increases with plasma density, reflecting Coulomb interaction screening by the plasma. We distinguish plasma-induced bleaching from genuine Rydberg blockade and discuss the interplay between time-resolved blockade and Rydberg exciton population dynamics.