Erlangen 2022 – scientific programme

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MO: Fachverband Molekülphysik

MO 5: Femtosecond Spectroscopy I

MO 5.6: Talk

Tuesday, March 15, 2022, 12:00–12:15, MO-H6

Measuring Interexcitonic Coherences in Semiconductor Nanocrystals using Coherent Two-Dimensional Fluorescence Spectroscopy — •Luisa Brenneis, Stefan Müller, and Tobias Brixner — Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

Quantum technologies require the availability of materials with controllable quantum coherences [1]. For this task, quantum dots are promising materials because their optoelectronic properties depend on their size and composition. However, characterizing coherent superpositions between excitonic states, i.e., interexcitonic coherences, is challenging in semiconductor nanocrystals because of overlapping spectral features and solvent contributions. Moreover, size and shape polydispersity leads to inhomogeneous broadening and ultrafast dephasing (15–25 fs) of interexcitonic coherences at room temperature [1,2].

To detect the ultrafast dynamics of interexcitonic coherences in CdSeS/ZnS quantum dots, we prepare coherences between several excitonic states using fluorescence-detected coherent two-dimensional electronic spectroscopy (F-2DES). Due to fluorescence detection, we achieve the absence of solvent contributions [3], which enables us to measure interexcitonic coherences at room temperature. We also investigate the possibility of F-2DES at low temperatures to decrease homogeneous broadening which would further simplify the analysis.

[1] E. Collini et. al., J. Phys. Chem. C 123, 31286–31293 (2019).

[2] D. B. Turner et. al., Nano Lett. 12, 880–886 (2012).

[3] S. Mueller et. al., ACS Nano 15, 4647–4657 (2021).