Tunable Emission Fine Structure and Origin of Quadratic TPA in 2D CdSe Nanoplatelets

Riccardo Scott^a, Judith Specht^b, Juan Climente^c, Marta Corona-Castro^b, Anatol Prudnikau^d, Artsiom Antanovich^d, Nina Owschimikow^a, Sotirios Christodoulou^e, Laurens Siebbeles^f, Michael Quick^a, Guilliaume Bertrand^g, Iwan Moreels^h, Mikhail Artemyev^d, Ulrike Woggon^a, Joseph Planelles^c, Marten Richter^b, Alexander Achtstein^a

^aInstitute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623, Berlin, Germany

^bTechnical University of Berlin (TU), Straße des 17. Juni, Berlin, Germany

^cUniversity Jaume I, Spain, Avinguda de Vicent Sos Baynat, Castelló de la Plana, Spain

^dBelarusian State University, Research Institute for Physical Chemistry Problems, Lenigradskaya Str. 14, Minsk, Belarus

^eICFO-Institut de Ciencies Fotoniques, 08860 Castelldefels (Barcelona), Spain.

^fDelft University of Technology, The Netherlands, Julianalaan, 136, Delft, Netherlands

^gCEA Saclay, 91191 Gif-sur-Yvette, France

^hGent University - BE, Krijgslaan 281 - S3, Gent, Belgium

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting19 (NFM19)

#Sol2D19. Two Dimensional Layered Semiconductors

Berlin, Germany, 2019 November 3rd - 8th

Organizers: Efrat Lifshitz, Cristiane Morais Smith and Doron Naveh

Oral, Alexander Achtstein, presentation 204
DOI: https://doi.org/10.29363/nanoge.nfm.2019.204
Publication date: 18th July 2019

We demonstrate a novel emission fine structure of the low temperature emission in II-VI nanoplatelets depending on the lateral size. Nanoplatelets are in an intermediate confinement regime with a rich substructure of excitons, which is neither quantum dot like nor like an ideal 2D exciton. We discuss the observed transition energies and relaxation dynamics of exciton states in CdSe platelets with varying lateral dimensions and compare them with a microscopic theoretical model including exciton-phonon scattering. The interplay of (lateral) confinement and Coulomb coupling in the intermediate regime results in strong changes with respect to simple weak or strong confinement models which are recovered by solving the full four dimensional lateral factorization free exciton wavefunction. A rich substructure of several exciton states is observed. We also demonstrate that the interplay of exciton bright and dark states provides principle insights into the overall temporal relaxation dynamics. Not only the linear properties of nanoplatelets are interesting, but also their nonlinear properties. In a second part we study the origin of the extremely high two photon absorption cross sections and their puzzling quadratic volume scaling. We show that excitonic correlation, wavefunction coherence and the related scaling of inter- and intraband transition dipole moments result in the observed quadratic volume dependence. Our results open up the possibility to engineer two photon absorbers with unprecedented cross sections and nonlinear optical applications at lowered intensities, like high sensitivity two photon autocorrelation.

References:

[1] R. Scott, A.W. Achtstein et al., Nanoscale 11, 3958 (2019)

[2] ] J.F. Specht, A.W. Achtstein, M. Richter et. al, Nanoscale (2019)

[3] A.W. Achtstein et al., ACS Nano 12, 9476−9483 (2018)

[4] ] J. Planelles, A.W. Achtstein et al., ACS Photonics 5, 3680 (2018)

[5] R. Scott, A.W. Achtstein et al., Nano Letters 15, 4985 (2015)

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