TY  - INPR
A1  - Huber, Bernhard
A1  - Pres, Sebastian
A1  - Wittmann, Emanuel
A1  - Dietrich, Lysanne
A1  - Lüttig, Julian
A1  - Fersch, Daniel
A1  - Krauss, Enno
A1  - Friedrich, Daniel
A1  - Kern, Johannes
A1  - Lisinetskii, Victor
A1  - Hensen, Matthias
A1  - Hecht, Bert
A1  - Bratschitsch, Rudolf
A1  - Riedle, Eberhard
A1  - Brixner, Tobias
T1  - Space- and time-resolved UV-to-NIR surface spectroscopy and 2D nanoscopy at 1 MHz repetition rate
N2  - We describe a setup for time-resolved photoemission electron microscopy (TRPEEM) with aberration correction enabling 3 nm spatial resolution and sub-20 fs temporal resolution. The latter is realized by our development of a widely tunable (215–970 nm) noncollinear optical parametric amplifier (NOPA) at 1 MHz repetition rate. We discuss several exemplary applications. Efficient photoemission from plasmonic Au nanoresonators is investigated with phase-coherent pulse pairs from an actively stabilized interferometer. More complex excitation fields are created with a liquid-crystal-based pulse shaper enabling amplitude and phase shaping of NOPA pulses with spectral components from 600 to 800 nm. With this system we demonstrate spectroscopy within a single plasmonic nanoslit resonator by spectral amplitude shaping and investigate the local field dynamics with coherent two-dimensional (2D) spectroscopy at the nanometer length scale (“2D nanoscopy”). We show that the local response varies across a distance as small as 33 nm in our sample. Further, we report two-color pump–probe experiments using two independent NOPA beamlines. We extract local variations of the excited-state dynamics of a monolayered 2D material (WSe2) that we correlate with low-energy electron microscopy (LEEM) and reflectivity (LEER) measurements. Finally, we demonstrate the in-situ sample preparation capabilities for organic thin films and their characterization via spatially resolved electron diffraction and dark-field LEEM.
KW  - Photoemission electron microscopy PEEM
KW  - Low energy electron microscopy LEEM
KW  - Spatially resolved 2D spectroscopy
KW  - Two-color pump-probe spectroscopy
KW  - Time-resolved photoemission electron microscopy
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191906
SN  - 0034-6748
N1  - This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Review of Scientific Instruments 90, 113103 (2019); https://doi.org/10.1063/1.5115322 and may be found at https://doi.org/10.1063/1.5115322.
ER  - 
TY  - JOUR
A1  - Li, Donghai
A1  - Shan, Hangyong
A1  - Rupprecht, Christoph
A1  - Knopf, Heiko
A1  - Watanabe, Kenji
A1  - Taniguchi, Takashi
A1  - Qin, Ying
A1  - Tongay, Sefaattin
A1  - Nuß, Matthias
A1  - Schröder, Sven
A1  - Eilenberger, Falk
A1  - Höfling, Sven
A1  - Schneider, Christian
A1  - Brixner, Tobias
T1  - Hybridized exciton-photon-phonon states in a transition-metal-dichalcogenide van-der-Waals heterostructure microcavity
JF  - Physical Review Letters
N2  - Excitons in atomically thin transition-metal dichalcogenides (TMDs) have been established as an attractive platform to explore polaritonic physics, owing to their enormous binding energies and giant oscillator strength. Basic spectral features of exciton polaritons in TMD microcavities, thus far, were conventionally explained via two-coupled-oscillator models. This ignores, however, the impact of phonons on the polariton energy structure. Here we establish and quantify the threefold coupling between excitons, cavity photons, and phonons. For this purpose, we employ energy-momentum-resolved photoluminescence and spatially resolved coherent two-dimensional spectroscopy to investigate the spectral properties of a high-quality-factor microcavity with an embedded WSe\(_2\) van-der-Waals heterostructure at room temperature. Our approach reveals a rich multi-branch structure which thus far has not been captured in previous experiments. Simulation of the data reveals hybridized exciton-photon-phonon states, providing new physical insight into the exciton polariton system based on layered TMDs.
KW  - strong coupling
KW  - laser spectroscopy
KW  - transition metal dichalcogenide
KW  - coherent multidimensional spectroscopy
KW  - exciton
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-351303
UR  - https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.087401
SN  - 1079-7114
ET  - accepted version
ER  -