Ultrafast solid-state quantum optics and nanophotonics

Prof. Dr. Rudolf Bratschitsch

Dr. Rudolf Bratschitsch

 

   


"Controlling light and matter on ultrafast and ultrasmall scales"


News


Together with the theory group of Ermin Malic (University of Marburg) we demonstrate dark exciton anti-funneling in strained atomically thin semiconductors.

Dark exciton anti-funneling in atomically thin semiconductors, R. Rosati, R. Schmidt, S. Brem, R. Perea-Causín, I. Niehues, J. Kern, J. Preuß , R. Schneider, S. Michaelis de Vasconcellos, R. Bratschitsch, and Ermin Malic, Nature Communications 12, 7221 (2021), Press Release (in German)

Iris Niehues has won the prize for the best PhD thesis of the year at the Department of Physics of the University of Münster. Dissertationspreis 2021 (in German).

© AG Bratschitsch

We have created large hBN nanocrystal arrays for photonic quantum technologies.

Assembly of large hBN nanocrystal arrays for quantum light emission, J. Preuß, E. Rudi, J. Kern, R. Schmidt, R. Bratschitsch, and S. Michaelis de Vasconcellos, 2D Materials 8,035005 (2021)

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© AG Bratschitsch

Together with the theory groups of Michael Rohlfing (University of Münster) and Daniel Wigger (Wroclaw University of Science and Technology, Poland) we show that the Stokes shift, i.e. the energy difference of optical absorption and emission, can be tuned by mechanical strain in atomatically thin semiconductors.

Strain tuning of the Stokes shift in atomically thin semiconductors, I. Niehues, P. Marauhn, T. Deilmann, D. Wigger, R. Schmidt, A. Arora, S. Michaelis de Vasconcellos, M. Rohlfing, and R. Bratschitsch, Nanoscale 12, 20786-20796 (2020)

Ashish Arora has won the Jury Poster prize and the Public Poster prize of the NOEKS15 conference.

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© AG Bratschitsch

Together with the group of Manfred Albrecht (University of Augsburg) we demonstrate that spin valves serve as ultrafast THz emitters, which can be switched with only a few milliTesla.

Spin valves as magnetically switchable spintronic THz emitters, M. Fix, R. Schneider, S. Michaelis de Vasconcellos, R. Bratschitsch, and M. Albrecht, Appl. Phys. Lett. 117, 132407 (2020)

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© A. Arora

Together with Thorsten Deilmann and Michael Rohlfing (University of Münster), Piotr Kossacki (University of Warsaw, Poland), and Marek Potemski (High magnetic field lab in Grenoble, France) we show that dark trions govern the optical absorption and photoluminescence of doped 2D semiconductors. In particular, we can pinpoint the exact energetic position of the dark trion states in monolayer MoS2, WS2, MoSe2, and WSe2.

Dark trions govern the temperature-dependent optical absorption and emission of doped atomically thin semiconductors, A. Arora, N. K. Wessling, T. Deilmann, T. Reichenauer, P. Steeger, P. Kossacki, M. Potemski, S. Michaelis de Vasconcellos, M. Rohlfing, and R. Bratschitsch, Phys. Rev. B 101, 241413 (2020)

Logo NOEKS15
© Dr. Daniel Wigger

The NOEKS15 (Nonlinear Optics and Excitation Kinetics in Semiconductors) conference will be held as an online event September 13-17, 2020.

The radio documentary on graphene and other 2D materials including our work on single-photon emitters can be found here: Deutschlandfunk Kultur (in German).

Physical Review Letter published

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© A. Arora

Together with the theory group of Thorsten Deilmann and Michael Rohlfing (University of Münster) we show that trions in the 2D semiconductor WS2 have an excited (2s) state.

Excited-state trions in monolayer WS2, A. Arora, T. Deilmann, T. Reichenauer, J. Kern, S. Michaelis de Vasconcellos, M. Rohlfing, and R. Bratschitsch, Phys. Rev. Lett. 123, 167401 (2019)

Applied Physics Letter published

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© R. Schneider

Together with the group of Manfred Albrecht (University of Augsburg) we present ultrafast spintronic THz emitters based on GdFe/Pt. They are substantially brighter than the previously investigated TbFe/Pt THz sources.

Spintronic GdFe/Pt THz emitters, R. Schneider, M. Fix, J. Bensmann, S. Michaelis de Vasconcellos, M. Albrecht, and R. Bratschitsch,  Appl. Phys. Lett. 115, 152401 (2019)

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© Torsten Stiehm

We have introduced a new experimental technique exploiting few-cycle femtosecond laser pulses to measure the nonlinear suceptibility of 2D materials over a broad spectral range.

Supercontinuum second harmonic generation spectroscopy of atomically thin semiconductors, T.Stiehm, R. Schneider, J. Kern, I. Niehues, S. Michaelis de Vasconcellos, and R. Bratschitsch, Rev. Sci. Instrum. 90, 083102 (2019)

Press coverage

Ashish Arora has received the EMFL prize of the European Magnetic Field Laboratory, recognizing his outstanding research in the physics of 2D materials in high magnetic fields.

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© Iris Niehues

We have revealed how excitons, which extend over two atomically thin sheets of a MoS2 bilayer ("interlayer excitons"), change their energy under uniaxial strain.

Interlayer excitons in bilayer MoS2 under uniaxial tensile strain, I. Niehues, A. Blob, T. Stiehm, S. Michaelis de Vasconcellos, and R. Bratschitsch, Nanoscale 11, 12788-12792 (2019)

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© Bratschitsch group

Together with the theory group of Tilmann Kuhn (University of Münster) and the Hübner company (Kassel) we have studied the impact of phonons on recently discovered localized light emitters in hexagonal boron nitride.

Phonon-assisted emission and absorption of individual color centers in hexagonal boron nitride, D. Wigger, R. Schmidt O. Del Pozo-Zamudio, J. Preuß, P. Tonndorf, R. Schneider, P. Steeger, J. Kern, Y. Khodaei, J. Sperling, S. Michaelis de Vasconcellos, R. Bratschitsch, and T. Kuhn, 2D Materials 6, 035006 (2019)

Iris Niehues shows high school students graphene
© Iris Niehues

Iris Niehues shows high school students how the thinnest material on earth (graphene) can be made by simple means at the Girl's day (28.03.2019).

Anna Blob has received the Best Poster Award at the "8th NRW Nano Conference" in Dortmund.

The next "International Conference on Nonlinear Optics and Excitation Kinetics in Semiconductors" (NOEKS 15) will be held in Münster in 2020.

Rudolf Bratschitsch gives a public lecture on the Nobel Prize in Physics 2010
© Daniel Wigger

Rudolf Bratschitsch gives a public lecture on the Nobel Prize in Physics 2010 (Graphene).

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© Bratschitsch group

Together with the group of Manfred Albrecht (University of Augsburg) we present ultrafast spintronic THz emitters based on TbFe/Pt. In particular, we show how the THz generation is governed by the composition of the ferrimagnet and the external magnetic field.

Magnetic-field-dependent THz emission of spintronic TbFe/Pt layers, R. Schneider, M. Fix, R. Heming, S. Michaelis de Vasconcellos, M. Albrecht, and R. Bratschitsch, ACS Photonics 5 (10), 3936-3942   (2018)

Ashish Arora has received the Best Poster Award at the "Flatlands Beyond Graphene 2018" conference in Leipzig.

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© Bratschitsch group

Together with the theory group of Michael Rohlfing (University of Münster) and the group of Marek Potemski (High magnetic field lab in Grenoble, France) we report on interlayer excitons in Se-based bulk transition metal dichalcogenides.

Valley-contrasting optics of interlayer excitons in Mo- and W-based bulk transition metal dichalcogenides, A. Arora, T. Deilmann, P. Marauhn, M. Drüppel, R. Schneider, M. R. Molas, D. Vaclavkova, S. Michaelis de Vasconcellos, M. Rohlfing, M. Potemski, and R. Bratschitsch, Nanoscale 10, 15571-15577 (2018)

Ashish Arora has received the Best Poster Award at the "3rd International Conference on 2D Crystals" in Malta.

Girls Day Logo
© www.girls-day.de

We will show high school students how the thinnest material on earth (graphene) can be made by simple means at the Girl's day.


2D Materials article published

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© Bratschitsch group

Together with the group of Marko Kralj (Institute of Physics, Croatia) we demonstrate that MoS2 monolayers grown by chemical vapor deposition (CVD) have the same mechanical properties as monolayers, which are exfoliated from natural molybdenite crystals. In CVD-grown monolayers, the applied tensile strain is fully transferred across grain boundaries between differently oriented monolayer crystal domains. Our work demonstrates that large-area CVD-grown MoS2 monolayers are promising for mass-produced nanomechanical devices. 

Strain transfer across grain boundaries in MoS2 monolayers grown by chemical vapor deposition, I. Niehues, A. Blob, T. Stiehm, R. Schmidt, ,

Logo DPG
© DPG

Together with Andres Castellanos-Gomez (Madrid), Thomas Heine (Leipzig), and Ulf Wiedwald (Duisburg-Essen) we organize the symposium "2D Materials" at the spring meeting of the German Physical Society (DPG) in Berlin, March 11-16, 2018.

Nature Communications and 2D Materials article published

Together with the theory groups of Ermin Malic (Chalmers University of Technology, Sweden) and Andreas Knorr (TU Berlin) we reveal a new type of coupling (Dexter-like) between states of equal spin in the K and K' valleys in a 2D semiconductor. It results in an inverted valley polarization and broadening of excitonic resonances.

Inverted valley polarization in optically excited transition metal dichalcogenides, G. Berghäuser, I. Bernal-Villamil, R. Schmidt, R. Schneider, I. Niehues, P. Erhart, S. Michaelis de Vasconcellos, R. Bratschitsch, A. Knorr, and E. Malic, Nature Communications 9, 971 (2018)

Exciton broadening and band renormalization due to Dexter-like intervalley coupling, I. Bernal-Villamil, G. Berghäuser, M. Selig, I. Niehues, R. Schmidt, R. Schneider, P. Tonndorf, P. Erhart, S. Michaelis de Vasconcellos, R. Bratschitsch, A. Knorr, and E. Malic,  2D Materials 5, 025011 (2018)

Nano Letter published

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© Bratschitsch group

Together with the groups of Michael Rohlfing (Münster), Ermin Malic (Chalmers University of Technology, Sweden), Andreas Knorr (TU Berlin), Tilmann Kuhn (Münster), and Andres Castellanos-Gomez (Madrid) we show that the excitonic line width in atomically thin semiconductors can be controlled by mechanical strain.

Strain control of exciton-phonon coupling in atomically thin semiconductors, I. Niehues, R. Schmidt, M. Drüppel, P. Marauhn, D. Christiansen, M. Selig, G. Berghäuser, D. Wigger, R. Schneider, L. Braasch, R. Koch, A. Castellanos-Gomez, T. Kuhn, A. Knorr, E. Malic, M. Rohlfing, S. Michaelis de Vasconcellos, and R. Bratschitsch, Nano Letters, DOI: 10.1021/acs.nanolett.7b04868 (2018)

Photo Robert Schneider, Johann Preuß, and Iris Niehues
© privat

Our PhD students Robert Schneider, Johann Preuß, and Iris Niehues (from left to right on photo) have attended the Alfried Krupp prize ceremony at the Villa Hügel in Essen. They met with previous awardees to discuss career paths in science and listened to the presentations of Immanuel Bloch (MPQ Munich) and this year's winner Alexander Szameit (University of Rostock).

OPON 2018

Logo OPON
© D. Wigger

We are co-organizing the 5th International Workshop on the Optical Properties of Nanostructures (OPON 2018) in Münster, 14-16 February 2018. The abstract submission deadline is 15 December 2017.

Physical Review Letter published

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© Bratschitsch group

Together with the theory groups of Andreas Knorr (TU Berlin) and Ermin Malic (Chalmers University of Technology, Sweden) we explain how exciton-phonon scattering governs the excitonic line shape of atomically thin semiconductors.

Phonon sidebands in monolayer transition metal dichalcogenides, D. Christiansen, M. Selig, G. Berghäuser, R. Schmidt, I. Niehues, R. Schneider, A. Arora, S. Michaelis de Vasconcellos, R. Bratschitsch, E. Malic, and A. Knorr Phys. Rev. Lett. 119, 187402 (2017)

Highlights der Physik

Booth at Highlights der Physik
© Bratschitsch group
Experiment at Highlights der Physik
© Bratschitsch group

We participated in the "Highlights der Physik" science fair (18-23 September 2017) in Münster with our booth about carbon structures (diamond, graphite, carbon nanotubes, fullerenes, and graphene).

Nature Communications published

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© Bratschitsch group

Together with the theory group of Michael Rohlfing (University of Münster) and Marek Potemski (High magnetic field lab in Grenoble, France) we report on interlayer excitons in a layered bulk semiconductor (MoTe2).

Interlayer excitons in a bulk van der Waals semiconductor, A. Arora, M. Drüppel, R. Schmidt, T. Deilmann, R. Schneider, M. R. Molas, P. Marauhn, S. Michaelis de Vasconcellos, M. Potemski, M. Rohlfing, and R. Bratschitsch Nature Communications 8, 639 (2017)

Nano Letters published

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© Bratschitsch group

Together with the groups of Wolfram Pernice (University of Münster) and Alexander Tartakovskii (University of Sheffield, UK) we have coupled a single-photon emitter in the layered semiconductor GaSe into a dielectric waveguide on a photonic chip.

On-chip waveguide coupling of a layered semiconductor single-photon source, P. Tonndorf, O. Del Pozo Zamudio, N. Gruhler, J. Kern, R. Schmidt, A. I. Dmitriev, A. P. Bakhtinov, A. I. Tartakovskii, W. HP Pernice, S. Michaelis de Vasconcellos, and R. Bratschitsch Nano Lett. 17, 5446 (2017)