Contact
Dr. Stephan Winnerl
Head Spectroscopy
s.winnerl
hzdr.de
Phone: +49 351 260 3522
Bachelor, Master, and Doctoral Theses
We are continuously looking for students to join our topics. If you are interested, please get in touch with the contact person listed or with Dr. Stephan Winnerl.
Carrier dynamics in graphene
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| Pump probe signals for different photon energies, corresponding microscopic calculations and energy diagram. As the photon energy is reduced to values below the optical phonon energy of about 200 meV, the relaxation is significantly slowed down. |
With the discovery of graphene, i.e. a single layer of hexagonally arranged carbon atoms featuring a gapless band structure with linear dispersion the research field of 2D materials has started. We study various materials, in particular graphene, transition metal dichalcogenides (TMDCs) and CrSBr. For graphene, the carrier dynamics of Dirac electrons, also Landau quantized graphene and graphene-based plasmonic samples is studied and we have developed graphene-based devices such as ultrafast broadband detectors. In TMDCs we look at ultrafast THz induced transitions within excitonic processes. Longstanding collaboration partners are Martin Mittendorff (University Duisburg-Essen) and Alexey Chernikov (TU Dresden).
Related publications
T. Venanzi, M. Cuccu, R. Perea-Causin, X. Sun, S. Brem, D. Erkensten, T. Taniguchi, K. Watanabe, E. Malic, M. Helm, S. Winnerl, and A. Chernikov, Ultrafast switching of trions in 2D materials by terahertz photons, Nature Photonics 18, 1344 (2024). See also press release.
J.W. Han, P. Sai, D.B. But, E. Uykur, S. Winnerl, G. Kumar, M.L. Chin, R.L. Myers-Ward, M.T. Dejarld, K.M. Daniels, T.E. Murphy, W. Knap, and M. Mittendorff, Strong transient magnetic fields induced by THz-driven plasmons in graphene disks, Nature Comm. 14, 7493 (2023). See also press release.
J. W. Han, M. L. Chin, S. Matschy, J. Poojali, A. Seidl, S. Winnerl, H. A. Hafez, D. Turchinovich, G. Kumar, R. L. Myers-Ward, M. T. Dejarld, K. M. Daniels, H. D. Drew, T. E. Murphy, M. Mittendorff, Plasmonic terahertz nonlinearity in graphene disks, Adv. Photonics Res. 3, 210021 (2022).
T. Venanzi, M. Selig, S. Winnerl, A. Pashkin, A. Knorr, M. Helm, H. Schneider, Terahertz induced energy transfer from hot carriers to trions in a MoSe2 monolayer, ACS Photonics 8, 2931 (2021).
D. B. But, M. Mittendorff, C. Consejo, F. Teppe, N. N. Mikhailov, S. A. Dvoretskii, C. Faugeras, S. Winnerl, M. Helm, W. Knap, M. Potemski, and M. Orlita, Suppressed Auger scattering and tunable light emission of Landau-quantized massless Kane electrons, Nature Photonics 13, (2019).
M. M. Jadidi, K. M. Daniels, R. L. Myers-Ward, D. K. Gaskill, J. C. König-Otto, S. Winnerl, A. B. Sushkov, H. D. Drew, T. E. Murphy, and M. Mittendorff, Optical Control of Plasmonic Hot Carriers in Graphene, ACS Photonics 6, 302 (2019).
F. Wendler, M. Mittendorff, J. C. König-Otto, S. Brem, C. Berger, W. A. de Heer, R. Böttger, H. Schneider, M. Helm, S. Winnerl, and E. Malic, Symmetry-Breaking Supercollisions in Landau-Quantized Graphene, Phys. Rev. Lett. 119, 067405 (2017).
J. C. König-Otto, M. Mittendorff, T. Winzer, F. Kadi, E. Malic, A. Knorr, C. Berger, W. A. de Heer, A. Pashkin, H. Schneider, M. Helm, and S. Winnerl, Slow noncollinear Coulomb scattering in the vicinity of the Dirac point in graphene, Phys. Rev. Lett. 117, 087401 (2016).
M. Mittendorff, F. Wendler, E. Malic, A. Knorr, M. Orlita, M. Potemski, C. Berger, W. A. de Heer, H. Schneider, M. Helm, and S. Winnerl, Carrier dynamics in Landau-quantized graphene featuring strong Auger scattering, Nature Physics 11, 75 (2015).
M. Mittendorff, S. Winnerl, J. Kamann, J. Eroms, D. Weiss, H. Schneider, and M. Helm, Ultrafast graphene-based broadband THz detector, Appl. Phys. Lett. 103, 021113 (2013).
S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W.A. de Heer, H. Schneider, and M. Helm, Carrier relaxation in epitaxial graphene photoexcited near the Dirac point, Phys. Rev. Lett. 107, 237401 (2011).
