@article{61523, abstract = {{AbstractMetasurface holography offers a powerful approach for manipulating wavefronts at the nano and micro scale. Extensive research has been conducted to enhance the multiplexing capacity for diverse wavefronts. However, the independence of multiplexed channels is fundamentally restricted in techniques using single‐layer metasurfaces, resulting in unavoidable crosstalk and the need for post‐filtering of the output wavefronts. Here, a universal wavefront multiplexing concept is presented based on non‐injective transformation. By employing joint optimization on two metasurfaces, different channels can be independently designed without any constraints on the output wavefronts. To validate this approach, ultra‐compact orbital angular momentum (OAM) sorters are designed. In these experiments, the output beams from different channels can be independently mapped to 2D positions with high fineness. In another application of wavefront‐multiplexed holography, 10‐channel multiplexing is experimentally achieved with minimal crosstalk and without the need for post‐processing. These results demonstrate the independence between channels enabled by the non‐injective transformation in the method. The precise wavefront control and high multiplexing capacity underscore its potential for scalable wavefront manipulation devices.}}, author = {{Jin, Xiao and Zentgraf, Thomas}}, issn = {{0935-9648}}, journal = {{Advanced Materials}}, publisher = {{Wiley}}, title = {{{Independent Wavefront Multiplexing with Metasurfaces via Non‐Injective Transformation}}}, doi = {{10.1002/adma.202511823}}, volume = {{38}}, year = {{2026}}, } @inproceedings{60022, author = {{Brauckmann, Michael and Narvaez Castaneda, Emmanuel and Siebert, Dustin and Brecht, Benjamin and Förstner, Jens and Zentgraf, Thomas}}, booktitle = {{Proceedings of The 15th International Conference on Metamaterials, Photonic Crystals and Plasmonics}}, location = {{Malaga, Spain}}, title = {{{Enhancement Of Light-matter Interaction In Topological Waveguides And Resonators}}}, year = {{2025}}, } @article{58606, author = {{Mathew, Albert and Aschwanden, Rebecca and Tripathi, Aditya and Jangid, Piyush and Sain, Basudeb and Zentgraf, Thomas and Kruk, Sergey}}, issn = {{1530-6984}}, journal = {{Nano Letters}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Nonreciprocal Metasurfaces with Epsilon-Near-Zero Materials}}}, doi = {{10.1021/acs.nanolett.4c06188}}, year = {{2025}}, } @article{60565, author = {{Bocchini, Adriana and Gerstmann, Uwe and Schmidt, Wolf Gero}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{10}}, publisher = {{American Physical Society (APS)}}, title = {{{Microscopic origin of gray tracks in KTiOPO4}}}, doi = {{10.1103/physrevb.111.104103}}, volume = {{111}}, year = {{2025}}, } @article{61245, author = {{Barkhausen, Franziska and Ares Santos, Laura and Schumacher, Stefan and Sperling, Jan}}, issn = {{2469-9926}}, journal = {{Physical Review A}}, number = {{3}}, publisher = {{American Physical Society (APS)}}, title = {{{Entanglement between dependent degrees of freedom: Quasiparticle correlations}}}, doi = {{10.1103/physreva.111.032404}}, volume = {{111}}, year = {{2025}}, } @article{61356, abstract = {{First-principles calculations reveal how topological defects in semiconducting carbon nanotubes trap triplet excitons and enable single-photon emission at telecom wavelengths, offering new insights into their potential for photonic devices.}}, author = {{Biktagirov, Timur and Gerstmann, Uwe and Schmidt, Wolf Gero}}, issn = {{2040-3364}}, journal = {{Nanoscale}}, number = {{11}}, pages = {{6884--6891}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Topological defects in semiconducting carbon nanotubes as triplet exciton traps and single-photon emitters}}}, doi = {{10.1039/d4nr03904a}}, volume = {{17}}, year = {{2025}}, } @article{62057, abstract = {{Abstract Time-resolved momentum microscopy is an emerging technique based on photoelectron spectroscopy for characterizing ultrafast electron dynamics and the out-of-equilibrium electronic structure of materials in the entire Brillouin zone with high efficiency. In this article, we introduce a setup for time-resolved momentum microscopy based on an energy-filtered momentum microscope coupled to a custom-made high-harmonic generation photon source driven by a multi-100 kHz commercial Yb-ultrafast laser that delivers fs pulses in the extreme ultraviolet range. The laser setup includes a nonlinear pulse compression stage employing spectral broadening in a Herriott-type bulk-based multi-pass cell. This element allows flexible tuning of the driving pulse duration, providing a versatile time-resolved momentum microscopy setup featuring two operational modes designed to enhance either the energy or time resolution. We show the capabilities of the system by tracing ultrafast electron dynamics in the conduction band valleys of a bulk crystal of the 2D semiconductor WS2. Using uncompressed driving laser pulses, we demonstrate an energy resolution better than (107 ± 2) meV, while compressed pulses lead to a time resolution better than (48.8 ± 17) fs.}}, author = {{Schiller, Karl Jakob and Sternemann, Lasse and Stupar, Matija and Omar, Alan and Hoffmann, Martin and Nitschke, Jonah Elias and Mischke, Valentin and Janas, David Maximilian and Ponzoni, Stefano and Zamborlini, Giovanni and Saraceno, Clara Jody and Cinchetti, Mirko}}, issn = {{2045-2322}}, journal = {{Scientific Reports}}, number = {{1}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Time-resolved momentum microscopy with fs-XUV photons at high repetition rates with flexible energy and time resolution}}}, doi = {{10.1038/s41598-025-86660-1}}, volume = {{15}}, year = {{2025}}, } @article{62059, author = {{Nitschke, Jonah Elias and Sternemann, Lasse and Gutnikov, Michael and Schiller, Karl and Coronado, Eugenio and Omar, Alan and Zamborlini, Giovanni and Saraceno, Clara and Stupar, Matija and Ruiz, Alberto M. and Esteras, Dorye L. and Baldoví, José J. and Anders, Frithjof and Cinchetti, Mirko}}, issn = {{2950-6360}}, journal = {{Newton}}, number = {{2}}, publisher = {{Elsevier BV}}, title = {{{Tracing the ultrafast buildup and decay of d-d transitions in FePS3}}}, doi = {{10.1016/j.newton.2025.100019}}, volume = {{1}}, year = {{2025}}, } @article{60568, author = {{Bocchini, Adriana and Kollmann, S. and Gerstmann, Uwe and Schmidt, Wolf Gero and Grundmeier, Guido}}, issn = {{0039-6028}}, journal = {{Surface Science}}, publisher = {{Elsevier BV}}, title = {{{Phosphonic acid adsorption on α-Bi2O3 surfaces}}}, doi = {{10.1016/j.susc.2025.122776}}, volume = {{760}}, year = {{2025}}, } @article{61353, abstract = {{Abstract Muonic hydrogen is an exotic atom where a muon instead of an electron is bound to a proton. The comparably high mass of the muon (≈ 207 · me ) has two important effects, (i) the reduced mass of the system becomes more important, and (ii) the muon is localized much closer to the nucleus. Thus, muonic hydrogen is not only excellently suitable for evaluating highly precise quantum electrodynamic (QED) calculations, but may also be used for assessing new approaches including finite nuclear size (FNS) effects to evaluate the proton structure and improve calculation schemes for the hyperfine splittings of many-particle systems, as e.g. to be implemented in density functional theory (DFT) software packages. Here, starting from Dirac’s equation we calculate the relativistic hyperfine splitting of the ground state and several excited states of muonic hydrogen analytically for different charge and magnetization models. The FNS related hyperfine shifts are compared with the differences between QED calculations and experimental measurements. This comparison also allows to unravel the role of the reduced mass, which is on one hand crucial in case of muonic atoms, but on the other hand is by no means well defined in relativistic quantum mechanics.}}, author = {{Franzke, Katharina L. and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{1742-6588}}, journal = {{Journal of Physics: Conference Series}}, number = {{1}}, publisher = {{IOP Publishing}}, title = {{{Finite-size and relativistic effects onto hyperfine interaction of muonic hydrogen}}}, doi = {{10.1088/1742-6596/3027/1/012001}}, volume = {{3027}}, year = {{2025}}, } @article{63160, author = {{Rose, Hendrik and Schumacher, Stefan and Meier, Torsten}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{24}}, publisher = {{American Physical Society (APS)}}, title = {{{Microscopic approach to the quantized light-matter interaction in semiconductor nanostructures: Complex coupled dynamics of excitons, biexcitons, and photons}}}, doi = {{10.1103/528f-7smh}}, volume = {{112}}, year = {{2025}}, } @article{60566, author = {{Bocchini, Adriana and Rüsing, Michael and Bollmers, Laura and Lengeling, Sebastian and Mues, Philipp and Padberg, Laura and Gerstmann, Uwe and Silberhorn, Christine and Eigner, Christof and Schmidt, Wolf Gero}}, issn = {{2475-9953}}, journal = {{Physical Review Materials}}, number = {{7}}, publisher = {{American Physical Society (APS)}}, title = {{{Mg dopants in lithium niobate: Defect models and impact on domain inversion}}}, doi = {{10.1103/5wz1-bjyr}}, volume = {{9}}, year = {{2025}}, } @inproceedings{55268, author = {{Rose, Hendrik and Sharapova, Polina R. and Meier, Torsten}}, booktitle = {{Ultrafast Phenomena and Nanophotonics XXVIII}}, editor = {{Betz, Markus and Elezzabi, Abdulhakem Y.}}, publisher = {{SPIE}}, title = {{{Microscopic simulations of the dynamics of excitonic many-body correlations coupled to quantum light}}}, doi = {{10.1117/12.2690245}}, year = {{2024}}, } @inproceedings{60023, author = {{Wetter, Helene and Gao, Wenlong and Rehberg, Falk and Wingenbach, Jan and Schumacher, Stefan and Zentgraf, Thomas}}, booktitle = {{Proceedings of The 14th International Conference on Metamaterials, Photonic Crystals and Plasmonics}}, issn = {{2429-1390}}, location = {{Toyama, Japan}}, title = {{{Dielectric metasurface for wave-vector variant and circular polarization dependent transmission}}}, year = {{2024}}, } @article{57410, author = {{Röder, J. and Gerhard, M. and Fuchs, C. and Stolz, W. and Heimbrodt, W. and Koch, M. and Ngo, C. and Steiner, J. T. and Meier, Torsten}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{19}}, publisher = {{American Physical Society (APS)}}, title = {{{Charge transfer magnetoexcitons in magnetoabsorption spectra of asymmetric type-II double quantum wells}}}, doi = {{10.1103/physrevb.110.195306}}, volume = {{110}}, year = {{2024}}, } @article{61255, abstract = {{Abstract Topological states have been widely investigated in different types of systems and lattices. In the present work, we report on topological edge states in double-wave (DW) chains, which can be described by a generalized Aubry-André-Harper (AAH) model. For the specific system of a driven-dissipative exciton polariton system we show that in such potential chains, different types of edge states can form. For resonant optical excitation, we further find that the optical nonlinearity leads to a multistability of different edge states. This includes topologically protected edge states evolved directly from individual linear eigenstates as well as additional edge states that originate from nonlinearity-induced localization of bulk states. Extending the system into two dimensions (2D) by stacking horizontal DW chains in the vertical direction, we also create 2D multi-wave lattices. In such 2D lattices multiple Su–Schrieffer–Heeger (SSH) chains appear along the vertical direction. The combination of DW chains in the horizonal and SSH chains in the vertical direction then results in the formation of higher-order topological insulator corner states. Multistable corner states emerge in the nonlinear regime.}}, author = {{Schneider, Tobias and Gao, Wenlong and Zentgraf, Thomas and Schumacher, Stefan and Ma, Xuekai}}, issn = {{2192-8614}}, journal = {{Nanophotonics}}, number = {{4}}, pages = {{509--518}}, publisher = {{Walter de Gruyter GmbH}}, title = {{{Topological edge and corner states in coupled wave lattices in nonlinear polariton condensates}}}, doi = {{10.1515/nanoph-2023-0556}}, volume = {{13}}, year = {{2024}}, } @article{61257, abstract = {{Exceptional points (EPs), with their intriguing spectral topology, have attracted considerable attention in a broad range of physical systems, with potential sensing applications driving much of the present research in this field. Here, we investigate spectral topology and EPs in systems with significant nonlinearity, exemplified by a nonequilibrium exciton-polariton condensate. With the possibility to control loss and gain and nonlinearity by optical means, this system allows for a comprehensive analysis of the interplay of nonlinearities (Kerr type and saturable gain) and non-Hermiticity. Not only do we find that EPs can be intentionally shifted in parameter space by the saturable gain, but we also observe intriguing rotations and intersections of Riemann surfaces and find nonlinearity-enhanced sensing capabilities. With this, our results illustrate the potential of tailoring spectral topology and related phenomena in non-Hermitian systems by nonlinearity. Published by the American Physical Society 2024 }}, author = {{Wingenbach, Jan and Schumacher, Stefan and Ma, Xuekai}}, issn = {{2643-1564}}, journal = {{Physical Review Research}}, number = {{1}}, publisher = {{American Physical Society (APS)}}, title = {{{Manipulating spectral topology and exceptional points by nonlinearity in non-Hermitian polariton systems}}}, doi = {{10.1103/physrevresearch.6.013148}}, volume = {{6}}, year = {{2024}}, } @article{61357, author = {{Krenz, Marvin and Sanna, Simone and Gerstmann, Uwe and Schmidt, Wolf Gero}}, issn = {{1932-7447}}, journal = {{The Journal of Physical Chemistry C}}, number = {{41}}, pages = {{17774--17778}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Understanding and Improving Triplet Exciton Transfer in Sensitized Silicon Solar Cells}}}, doi = {{10.1021/acs.jpcc.4c05446}}, volume = {{128}}, year = {{2024}}, } @article{54868, abstract = {{AbstractMost properties of solid materials are defined by their internal electric field and charge density distributions which so far are difficult to measure with high spatial resolution. Especially for 2D materials, the atomic electric fields influence the optoelectronic properties. In this study, the atomic‐scale electric field and charge density distribution of WSe2 bi‐ and trilayers are revealed using an emerging microscopy technique, differential phase contrast (DPC) imaging in scanning transmission electron microscopy (STEM). For pristine material, a higher positive charge density located at the selenium atomic columns compared to the tungsten atomic columns is obtained and tentatively explained by a coherent scattering effect. Furthermore, the change in the electric field distribution induced by a missing selenium atomic column is investigated. A characteristic electric field distribution in the vicinity of the defect with locally reduced magnitudes compared to the pristine lattice is observed. This effect is accompanied by a considerable inward relaxation of the surrounding lattice, which according to first principles DFT calculation is fully compatible with a missing column of Se atoms. This shows that DPC imaging, as an electric field sensitive technique, provides additional and remarkable information to the otherwise only structural analysis obtained with conventional STEM imaging.}}, author = {{Groll, Maja and Bürger, Julius and Caltzidis, Ioannis and Jöns, Klaus D. and Schmidt, Wolf Gero and Gerstmann, Uwe and Lindner, Jörg K. N.}}, issn = {{1613-6810}}, journal = {{Small}}, publisher = {{Wiley}}, title = {{{DFT‐Assisted Investigation of the Electric Field and Charge Density Distribution of Pristine and Defective 2D WSe2 by Differential Phase Contrast Imaging}}}, doi = {{10.1002/smll.202311635}}, year = {{2024}}, } @article{54856, abstract = {{Abstract Theoretical spectroscopy based on double perturbation theory is typically challenged by systems with large orbital hyperfine splitting. Therefore, we here derive a rigorous, non-perturbative scheme starting from Dirac’s equation which allows to calculate the contribution of the orbital HFI for complex structures including heavy atoms with strong spin-orbit coupling (SOC). Using the PAW formalism, the method has been implemented in the software package Quantum ESPRESSO. We show that the ‘orbital part’ actually scales with SOC strength if orbital quenching is hindered by low local symmetry, i.e. in case of dimers or atoms at surfaces. This holds true in particular when the unpaired electron is localized in quasi-atomic p-like orbitals. Here, the orbital part is by far not negligible, but becomes dominant by surpassing the dipolar contribution by a factor of five.}}, author = {{Franzke, Katharina and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{1742-6588}}, journal = {{Journal of Physics: Conference Series}}, number = {{1}}, publisher = {{IOP Publishing}}, title = {{{Relativistic calculation of the orbital hyperfine splitting in complex microscopic structures}}}, doi = {{10.1088/1742-6596/2701/1/012094}}, volume = {{2701}}, year = {{2024}}, }