In collaboration with the group of Ermin Malic (University of Marburg), we used ultrafast near-field microscopy to study the Mott transition of strongly-bound excitons in an atomically thin heterostructure of WSe2, unveiling pronounced nanoscale modulation in the dynamics of the transition. These findings underscore how nanoscale disorder plays a pivotal role in the dynamics of many-body phase transitions within a broad range of van der Waals materials.
Collaborating with partners from Germany, France, UK and Sweden we observed high-order terahertz nonlinearities directly in a free-running quantum cascade laser. With field-resolved two-dimensional spectroscopy we revealed up to eight-wave-mixing processes in a regime of negative absorption as well as the laser’s sub-cycle gain dynamics. High-order nonlinearities of this kind have the potential for various future applications, ranging from efficient intracavity frequency conversion and mode proliferation to passive mode locking.
The Ministry of Science and Technology of Taiwan has awarded our former team member and close collaborator Chaw-Keong Yong, who was recently appointed assistant professor at National Taiwan University, with the Columbus research grant. This fellowship recognises his work on 2D quantum materials and ultrafast optical spectroscopy as well as his extensive collaborative works with scientists across the world. The grant provides Prof. Chaw-Keong Yong with the opportunity to establish a competitive research group exploring quantum optoelectronic properties of atomically thin materials using ultrafast optical microscopy.
Dr. Fabian Mooshammer has received the "Kulturpreis Bayern" for his PhD Thesis "Multi-terahertz nanotomography of van der Waals quantum materials". The prize honours people who enrich our society with their commitment, their work and their enthusiasm for art, culture and science....
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Together with the groups of Klaus Richter (UR), Ferdinand Evers (UR), Ulrich H?fer (University of Marburg) and collaborators from the Novosibirsk State University, we discovered a novel generation mechanism of high-order harmonics in the surface state of a topological insulator. When quasi-relativistic electrons are accelerated through the Dirac point by an intense lightwave, they abruptly reverse their velocity allowing for purely non-integer high-harmonic generation. The lightwave-driven currents reveal intriguing aspects of the quantum mechanical nature of electrons in topological matter.
Press release (idw) in German
Press release (idw) in English
The results have been published in Nature....
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In collaboration with the group of Jaroslav Fabian (UR) and together with Tyler Cocker and Jessica Boland, we implemented a novel concept to map out ultrafast interlayer tunneling and recombination dynamics of excitons in van der Waals heterostructures in a contact-free manner. The new technique provides spatiotemporal access to tunnelling processes in insulating, conducting, or superconducting systems, on nanometer length and femtosecond time scales, conceptually bridging the gap between near-field microscopy and light-wave driven STM.
Press release (idw) in German
Press release (idw) in English
Fabian Mooshammer received the PhD award by the German terahertz center (Deutsches Terahertzzentrum e.V.) for his thesis "Multi-terahertz nanotomography of van der Waals quantum materials". The biennial award was conferred in the annual meeting on May 7....
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Together with the groups of Dominique Bougeard (UR) and Cristiano Ciuti (Université de Paris), we explored a novel regime of light-matter interaction, where both the Rabi frequency induced by a coherent driving field and the vacuum Rabi frequency set by a cavity field are comparable to the carrier frequency of light. The resulting subcycle nonlinearities may facilitate novel nonclassical light sources, quantum phase transitions, or cavity chemistry with virtual photons.
We are pleased to announce the launch of our new RUN website: https://www.run-regensburg.com/
The new website offers quick and easy access to essential information on the RUN, dates, availability, press releases, construction progress, publications, and open positions.
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In a collaboration with the group of Ermin Malic (University of Marburg), we demonstrated proximity-controlled strong-coupling between phonons and electrically neutral excitons at atomically sharp interfaces of WSe2/gypsum heterostructures, creating new exciton-phonon mixed eigenmodes, called excitonic Lyman polarons. These findings could enable new man-made phase transitions in artificially stacked materials.
Press release (idw) in German
Press release (idw) in English
Press release (Science X) in English
The new career guide Research in Bavaria features job opportunities and stories on pioneering research at the University of Regensburg. Meet our researchers and learn more about your career opportunities at the University of Regensburg.
See also the feature article on our group The Quantum World in Motion....
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Together with our long-term collaborators Mack Kira (University of Michigan, Ann Arbor) and Stephan W. Koch (Philipps Universit?t Marburg), we have developed an all-optical way of mapping out electronic band structures of even tiny flakes of quantum materials in ambient air. Our approach uses a new concept called momentum combs to achieve super-resolution, which could help us to tailor emerging quantum materials and pave the way for advanced energy technologies and quantum computers.
Press release (idw) in English
Press release (idw) in German
In close collaboration with the groups of Jascha Repp (UR) and Angel Rubio (Max Planck Institute for the Structure and Dynamics of Matter, Hamburg), we found a way to map out atom-scale lightwave dynamics. Using a single-molecule switch, which senses changes in the local electromagnetic fields, we were able to quantitatively detect atom-scale near-field waveforms in the junction of a scanning tunneling microscope.
Together with our collaborators from Jascha Repp's group and Nikolaj Moll, we have found a fascinating way to push a select atom with controlled forces so quickly that we can choreograph the motion of a single molecule within less than a trillionth of a second.
The results have been published in Nature....
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Together with the groups of Prof. Dr. Miriam S. Vitiello (Pisa) and Prof. Dr. Edmund Linfield (Leeds) we developed a new group of saturable absorbers in the terahertz spectral domain based on ultra-strong coupling of intersubband transitions to the resonant mode of a microresonator. These new devices could enable passive mode locking of future quantum cascade lasers.
In collaboration with the group of Ermin Malic (University of Marburg), we used ultrafast near-field microscopy to study the Mott transition of strongly-bound excitons in an atomically thin heterostructure of WSe2, unveiling pronounced nanoscale modulation in the dynamics of the transition. These findings underscore how nanoscale disorder plays a pivotal role in the dynamics of many-body phase transitions within a broad range of van der Waals materials.
Collaborating with partners from Germany, France, UK and Sweden we observed high-order terahertz nonlinearities directly in a free-running quantum cascade laser. With field-resolved two-dimensional spectroscopy we revealed up to eight-wave-mixing processes in a regime of negative absorption as well as the laser’s sub-cycle gain dynamics. High-order nonlinearities of this kind have the potential for various future applications, ranging from efficient intracavity frequency conversion and mode proliferation to passive mode locking.
