@article{61253, abstract = {{In the SUPER scheme (Swing-UP of the quantum EmitteR population), excitation of a quantum emitter is achieved with two off-resonant, red-detuned laser pulses. This allows the generation of high-quality single photons without the need of complex laser stray light suppression or careful spectral filtering. In the present work, we extend this promising method to quantum emitters, specifically semiconductor quantum dots, inside a resonant optical cavity. A significant advantage of the SUPER scheme is identified in that it eliminates re-excitation of the quantum emitter by suppressing photon emission during the excitation cycle. This, in turn, leads to almost ideal single-photon purity, overcoming a major factor typically limiting the quality of photons generated with quantum emitters in high-quality cavities. We further find that for cavity-mediated biexciton emission of degenerate photon pairs, the SUPER scheme leads to near-perfect biexciton initialization with very high values of polarization entanglement of emitted photon pairs. Published by the American Physical Society 2024 }}, author = {{Heinisch, Nils and Köcher, Nikolas and Bauch, David and Schumacher, Stefan}}, issn = {{2643-1564}}, journal = {{Physical Review Research}}, number = {{1}}, publisher = {{American Physical Society (APS)}}, title = {{{Swing-up dynamics in quantum emitter cavity systems: Near ideal single photons and entangled photon pairs}}}, doi = {{10.1103/physrevresearch.6.l012017}}, volume = {{6}}, 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{61259, author = {{Bauch, Fabian and Dong, Chuan-Ding and Schumacher, Stefan}}, issn = {{1932-7447}}, journal = {{The Journal of Physical Chemistry C}}, number = {{8}}, pages = {{3525--3532}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Dynamics of Electron–Hole Coulomb Attractive Energy and Dipole Moment of Hot Excitons in Donor–Acceptor Polymers}}}, doi = {{10.1021/acs.jpcc.3c07513}}, volume = {{128}}, year = {{2024}}, } @article{61263, abstract = {{Charge transfer mechanism in the deprotonation-induced n-type doping of PCBM.}}, author = {{Dong, Chuan-Ding and Bauch, Fabian and Hu, Yuanyuan and Schumacher, Stefan}}, issn = {{1463-9076}}, journal = {{Physical Chemistry Chemical Physics}}, number = {{5}}, pages = {{4194--4199}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Charge transfer in superbase n-type doping of PCBM induced by deprotonation}}}, doi = {{10.1039/d3cp05105f}}, volume = {{26}}, 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}}, } @inbook{62067, abstract = {{Most FPGA boards in the HPC domain are well-suited for parallel scaling because of the direct integration of versatile and high-throughput network ports. However, the utilization of their network capabilities is often challenging and error-prone because the whole network stack and communication patterns have to be implemented and managed on the FPGAs. Also, this approach conceptually involves a trade-off between the performance potential of improved communication and the impact of resource consumption for communication infrastructure, since the utilized resources on the FPGAs could otherwise be used for computations. In this work, we investigate this trade-off, firstly, by using synthetic benchmarks to evaluate the different configuration options of the communication framework ACCL and their impact on communication latency and throughput. Finally, we use our findings to implement a shallow water simulation whose scalability heavily depends on low-latency communication. With a suitable configuration of ACCL, good scaling behavior can be shown to all 48 FPGAs installed in the system. Overall, the results show that the availability of inter-FPGA communication frameworks as well as the configurability of framework and network stack are crucial to achieve the best application performance with low latency communication.}}, author = {{Meyer, Marius and Kenter, Tobias and Petrica, Lucian and O’Brien, Kenneth and Blott, Michaela and Plessl, Christian}}, booktitle = {{Lecture Notes in Computer Science}}, isbn = {{9783031697654}}, issn = {{0302-9743}}, publisher = {{Springer Nature Switzerland}}, title = {{{Optimizing Communication for Latency Sensitive HPC Applications on up to 48 FPGAs Using ACCL}}}, doi = {{10.1007/978-3-031-69766-1_9}}, year = {{2024}}, } @article{56604, abstract = {{This manuscript makes the claim of having computed the 9th Dedekind number, D(9). This was done by accelerating the core operation of the process with an efficient FPGA design that outperforms an optimized 64-core CPU reference by 95x. The FPGA execution was parallelized on the Noctua 2 supercomputer at Paderborn University. The resulting value for D(9) is 286386577668298411128469151667598498812366. This value can be verified in two steps. We have made the data file containing the 490 M results available, each of which can be verified separately on CPU, and the whole file sums to our proposed value. The paper explains the mathematical approach in the first part, before putting the focus on a deep dive into the FPGA accelerator implementation followed by a performance analysis. The FPGA implementation was done in Register-Transfer Level using a dual-clock architecture and shows how we achieved an impressive FMax of 450 MHz on the targeted Stratix 10 GX 2,800 FPGAs. The total compute time used was 47,000 FPGA hours.}}, author = {{Van Hirtum, Lennart and De Causmaecker, Patrick and Goemaere, Jens and Kenter, Tobias and Riebler, Heinrich and Lass, Michael and Plessl, Christian}}, issn = {{1936-7406}}, journal = {{ACM Transactions on Reconfigurable Technology and Systems}}, number = {{3}}, pages = {{1--28}}, publisher = {{Association for Computing Machinery (ACM)}}, title = {{{A Computation of the Ninth Dedekind Number Using FPGA Supercomputing}}}, doi = {{10.1145/3674147}}, volume = {{17}}, year = {{2024}}, } @inproceedings{53503, author = {{Olgu, Kaan and Kenter, Tobias and Nunez-Yanez, Jose and Mcintosh-Smith, Simon}}, booktitle = {{Proceedings of the 12th International Workshop on OpenCL and SYCL}}, publisher = {{ACM}}, title = {{{Optimisation and Evaluation of Breadth First Search with oneAPI/SYCL on Intel FPGAs: from Describing Algorithms to Describing Architectures}}}, doi = {{10.1145/3648115.3648134}}, year = {{2024}}, } @inbook{62916, author = {{Zhang, Hongdan and Zuo, Ruixin and Yang, Shidong and Trautmann, Alexander and Song, Xiaohong and Meier, Torsten and Yang, Weifeng}}, booktitle = {{High-Order Harmonic Generation in Solids}}, isbn = {{9789811279553}}, publisher = {{WORLD SCIENTIFIC}}, title = {{{Analyzing High-Order Harmonic Generation in Solids Based on Semi-Classical Recollision Models}}}, doi = {{10.1142/9789811279560_0006}}, year = {{2024}}, } @inbook{62917, author = {{Reichelt, Matthias and Zuo, Ruixin and Song, Xiaohong and Yang, Weifeng and Meier, Torsten}}, booktitle = {{High-Order Harmonic Generation in Solids}}, isbn = {{9789811279553}}, publisher = {{WORLD SCIENTIFIC}}, title = {{{High-Order Harmonic Generation in Semiconductors with Excitonic Effects}}}, doi = {{10.1142/9789811279560_0009}}, year = {{2024}}, } @misc{62915, author = {{Meier, Torsten and Ali, Usman and Holthaus, Martin}}, publisher = {{LibreCat University}}, title = {{{Floquet dynamics of ultracold atoms in optical lattices with a parametrically modulated trapping potential}}}, doi = {{10.5281/ZENODO.11935146}}, 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}}, } @article{54866, author = {{Diederich, Jonathan and Velasquez Rojas, Jennifer and Zare Pour, Mohammad Amin and Ruiz Alvarado, Isaac Azahel and Paszuk, Agnieszka and Sciotto, Rachele and Höhn, Christian and Schwarzburg, Klaus and Ostheimer, David and Eichberger, Rainer and Schmidt, Wolf Gero and Hannappel, Thomas and van de Krol, Roel and Friedrich, Dennis}}, issn = {{0002-7863}}, journal = {{Journal of the American Chemical Society}}, number = {{13}}, pages = {{8949--8960}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Unraveling Electron Dynamics in p-type Indium Phosphide (100): A Time-Resolved Two-Photon Photoemission Study}}}, doi = {{10.1021/jacs.3c12487}}, volume = {{146}}, year = {{2024}}, } @article{54855, abstract = {{Density-functional theory calculations on P-rich InP(001):H surfaces are presented. Depending on temperature, pressure and substrate doping, hydrogen desorption or adsorption will occur and influence the surface electronic properties. For p-doped samples, the charge transition levels of the P dangling bond defects resulting from H desorption will lead to Fermi level pinning in the lower half of the band gap. This explains recent experimental data. For n-doped substrates, H-deficient surfaces are the ground-state structure. This will lead to Fermi level pinning below the bulk conduction band minimum. Surface defects resulting from the adsorption of additional hydrogen can be expected as well, but affect the surface electronic properties less than H desorption.}}, author = {{Sciotto, Rachele and Ruiz Alvarado, Isaac Azahel and Schmidt, Wolf Gero}}, issn = {{2571-9637}}, journal = {{Surfaces}}, number = {{1}}, pages = {{79--87}}, publisher = {{MDPI AG}}, title = {{{Substrate Doping and Defect Influence on P-Rich InP(001):H Surface Properties}}}, doi = {{10.3390/surfaces7010006}}, volume = {{7}}, year = {{2024}}, } @article{54869, author = {{Pfnür, H. and Tegenkamp, C. and Sanna, S. and Jeckelmann, E. and Horn-von Hoegen, M. and Bovensiepen, U. and Esser, N. and Schmidt, Wolf Gero and Dähne, M. and Wippermann, S. and Bechstedt, F. and Bode, M. and Claessen, R. and Ernstorfer, R. and Hogan, C. and Ligges, M. and Pucci, A. and Schäfer, J. and Speiser, E. and Wolf, M. and Wollschläger, J.}}, issn = {{0167-5729}}, journal = {{Surface Science Reports}}, number = {{2}}, publisher = {{Elsevier BV}}, title = {{{Atomic wires on substrates: Physics between one and two dimensions}}}, doi = {{10.1016/j.surfrep.2024.100629}}, volume = {{79}}, year = {{2024}}, } @article{54865, author = {{Krenz, Marvin and Gerstmann, Uwe and Schmidt, Wolf Gero}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, number = {{7}}, publisher = {{American Physical Society (APS)}}, title = {{{Defect-Assisted Exciton Transfer across the Tetracene-Si(111):H Interface}}}, doi = {{10.1103/physrevlett.132.076201}}, volume = {{132}}, year = {{2024}}, } @article{62868, abstract = {{We theoretically investigate strategies for the deterministic creation of trains of time-bin entangled photons using an individual quantum emitter described by a Λ-type electronic system. We explicitly demonstrate the theoretical generation of linear cluster states with substantial numbers of entangled photonic qubits in full microscopic numerical simulations. The underlying scheme is based on the manipulation of ground state coherences through precise optical driving. One important finding is that the most easily accessible quality metrics, the achievable rotation fidelities, fall short in assessing the actual quantum correlations of the emitted photons in the face of losses. To address this, we explicitly calculate stabilizer generator expectation values as a superior gauge for the quantum properties of the generated many-photon state. With widespread applicability in other emitter and excitation–emission schemes also, our work lays the conceptual foundations for an in-depth practical analysis of time-bin entanglement based on full numerical simulations with predictive capabilities for realistic systems and setups, including losses and imperfections. The specific results shown in the present work illustrate that with controlled minimization of losses and realistic system parameters for quantum-dot type systems, useful linear cluster states of significant lengths can be generated in the calculations, discussing the possibility of scalability for quantum information processing endeavors.}}, author = {{Bauch, David and Köcher, Nikolas and Heinisch, Nils and Schumacher, Stefan}}, issn = {{2835-0103}}, journal = {{APL Quantum}}, number = {{3}}, publisher = {{AIP Publishing}}, title = {{{Time-bin entanglement in the deterministic generation of linear photonic cluster states}}}, doi = {{10.1063/5.0214197}}, volume = {{1}}, year = {{2024}}, } @article{62942, abstract = {{AbstractNanostructured bilayer thin films with superhydrophobic and superhydrophilic surfaces were prepared using Ti6Al4V alloy substrates which allowed for the comparative analysis of polyvinyl acetate (PVAc) particle adsorption as a function of the interface structure. The PVAc particles were obtained from emulsion polymerization of vinyl acetate. A superhydrophilic TiO2 nanofiber-based 3D network was created on the Ti6Al4V alloy substrate by application of a hydrothermal method. Subsequent UV-grafting of ultra-thin polydimethylsiloxane (PDMS) layers resulted in a superhydrophobic surface. The modification steps were followed via Diffuse Reflectance Infrared Fourier Transform Spectroscopy, X-ray Photoelectron Spectroscopy, Field Emission-Scanning Electron Microscopy, contact angle and Electrochemical Impedance Spectroscopy. A mechanism for the adsorption of PVAc at the two electrolyte/substrate interfaces could be revealed.}}, author = {{Neßlinger, Vanessa and Atlanov, Jan and Grundmeier, Guido}}, issn = {{3004-9261}}, journal = {{Discover Applied Sciences}}, number = {{6}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Interactions of polyvinyl acetate dispersions with nanostructured superhydrophilic and superhydrophobic Ti6Al4V alloy surfaces}}}, doi = {{10.1007/s42452-024-05916-z}}, volume = {{6}}, year = {{2024}}, }