@article{61249, author = {{Ai, Qiang and Wingenbach, Jan and Yang, Xinmiao and Wei, Jing and Hatzopoulos, Zaharias and Savvidis, Pavlos G. and Schumacher, Stefan and Ma, Xuekai and Gao, Tingge}}, issn = {{2331-7019}}, journal = {{Physical Review Applied}}, number = {{2}}, publisher = {{American Physical Society (APS)}}, title = {{{Optically and remotely controlling localization of exciton-polariton condensates in a potential lattice}}}, doi = {{10.1103/physrevapplied.23.024029}}, volume = {{23}}, year = {{2025}}, } @article{61351, abstract = {{AbstractThe interaction of water molecules with semiconductor surfaces is relevant to various optoelectronic phenomena and physicochemical processes. Despite advances in fundamental understanding of water‐exposed surfaces, the detailed time‐ and energy‐resolved behavior of excited electrons remains largely unexplored. Here, the effects of water exposure on the near‐surface electron dynamics of phosphorus‐terminated p(2×2)/c(4×2)‐reconstructed indium phosphide (100) (P‐rich InP) are studied experimentally and matched to theoretical calculations. The P‐rich InP surface, consisting of H‐passivated P‐dimers, serves as a model for other P‐containing III‐V semiconductors such as gallium phosphide (GaP) or aluminum indium phosphide (AlInP). Electron dynamics near the surface are probed with femtosecond resolution using time‐resolved two‐photon photoemission (tr‐2PPE), a pump‐probe spectroscopic technique. Pulsed water exposure preserves electronic states and significantly increases lifetimes at the conduction band minimum (CBM). Density‐functional theory (DFT) calculations attribute these findings to suppression of surface vibrational modes in the top P‐layer by water exposure, reducing electronic transition probabilities of near‐band‐gap surface states. The results suggest that many near‐surface state lifetimes reported in ultra‐high vacuum may change significantly upon electrolyte exposure. These states may thus contribute more strongly to surface reactions than traditionally assumed. Demonstrating this effect for the technologically relevant P‐rich InP surface opens new opportunities in this underexplored area of surface electrochemistry.}}, author = {{Diederich, Jonathan and Paszuk, Agnieszka and Ruiz Alvarado, Isaac Azahel and Krenz, Marvin and Zare Pour, Mohammad Amin and Babu, Diwakar Suresh and Velazquez Rojas, Jennifer and Höhn, Christian and Gao, Yuying and Schwarzburg, Klaus and Ostheimer, David and Eichberger, Rainer and Schmidt, Wolf Gero and Hannappel, Thomas and de Krol, Roel van and Friedrich, Dennis}}, issn = {{2196-7350}}, journal = {{Advanced Materials Interfaces}}, number = {{16}}, publisher = {{Wiley}}, title = {{{Ultrafast Electron Dynamics at the Water‐Modified InP(100) Surface}}}, doi = {{10.1002/admi.202500463}}, volume = {{12}}, 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{58519, abstract = {{A unified theoretical approach to describe the properties of multimode squeezed light generated in a lossy medium is presented. This approach is valid for Markovian environments and includes both a model of discrete losses based on the beamsplitter approach and a generalized continuous loss model based on the spatial Langevin equation. For an important class of Gaussian states, we derive master equations for the second-order correlation functions and illustrate their solution for both frequency-independent and frequency-dependent losses. Studying the mode structure, we demonstrate that in a lossy environment no broadband basis without quadrature correlations between the different broadband modes exists. Therefore, various techniques and strategies to introduce broadband modes can be considered. We show that the Mercer expansion and the Williamson-Euler decomposition do not provide modes in which the maximal squeezing contained in the system can be measured. In turn, we find a new broadband basis that maximizes squeezing in the lossy system and present an algorithm to construct it.}}, author = {{Kopylov, Denis A. and Meier, Torsten and Sharapova, Polina R.}}, issn = {{2521-327X}}, journal = {{Quantum}}, publisher = {{Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften}}, title = {{{Theory of Multimode Squeezed Light Generation in Lossy Media}}}, doi = {{10.22331/q-2025-02-04-1621}}, volume = {{9}}, year = {{2025}}, } @article{62034, abstract = {{Effective single-particle theories, such as Hartree–Fock, density functional theory, and tight-binding, are limited by the computational cost of the self-consistent field (SCF) procedure, which typically scales cubically with the system size. This makes large-scale applications impractical without specialized algorithms and hardware. Here, we present the submatrix and graphical processing unit (GPU)-accelerated software implementation of the PTB tight-binding potential, realized in the open-source ptb codebase [M. Mueller, A. Katbashev, and S. Ehlert (2025). “grimme-lab/ptb: v3.8.1,” Zenodo. https://zenodo.org/records/17015872]. We first benchmark a traditional diagonalization-based SCF solver against density-matrix-based purification approaches, systematically varying both system size and computer hardware. Our findings show that the usage of GPUs permits shifting the boundaries to much larger systems than previously thought feasible, achieving an overall 10–15-fold performance speedup. Second, we introduce the implementation of a decomposition-type submatrix method, specifically designed for efficient operation on mid- to large-sized systems, to address the computational overhead associated with full-system diagonalization. We demonstrate that, from a certain dimension (≈104 basis functions) on, our submatrix method reduces the overall computational cost while maintaining acceptable numerical accuracy. Our study demonstrates the significance of the interplay between modern hardware, algorithmic considerations, and novel tight-binding methods, paving the way for further development in this direction.}}, author = {{Katbashev, Abylay and Schade, Robert and Laß, Michael and Müller, Marcel and Grimme, Stefan and Hansen, Andreas and Kühne, Thomas}}, issn = {{0021-9606}}, journal = {{The Journal of Chemical Physics}}, number = {{13}}, publisher = {{AIP Publishing}}, title = {{{Submatrix and GPU-accelerated implementation of density matrix tight-binding}}}, doi = {{10.1063/5.0271379}}, volume = {{163}}, year = {{2025}}, } @inproceedings{62066, abstract = {{In the context of high-performance computing (HPC) for distributed workloads, individual field-programmable gate arrays (FPGAs) need efficient ways to exchange data, which requires network infrastructure and software abstractions. Dedicated multi-FPGA clusters provide inter-FPGA networks for direct device to device communication. The oneAPI high-level synthesis toolchain offers I/O pipes to allow user kernels to interact with the networking ports of the FPGA board. In this work, we evaluate using oneAPI I/O pipes for direct FPGA-to-FPGA communication by scaling a SYCL implementation of a Jacobi solver on up to 25 FPGAs in the Noctua 2 cluster. We see good results in weak and strong scaling experiments.}}, author = {{Alt, Christoph and Plessl, Christian and Kenter, Tobias}}, booktitle = {{Proceedings of the 13th International Workshop on OpenCL and SYCL}}, isbn = {{9798400713606}}, keywords = {{Multi-FPGA, High-level Synthesis, oneAPI, FPGA}}, publisher = {{Association for Computing Machinery}}, title = {{{Evaluating oneAPI I/O Pipes in a Case Study of Scaling a SYCL Jacobi Solver to multiple FPGAs}}}, doi = {{10.1145/3731125.3731131}}, year = {{2025}}, } @inproceedings{62065, author = {{Sundriyal, Shivam and Büttner, Markus and Alt, Christoph and Kenter, Tobias and Aizinger, Vadym}}, booktitle = {{2025 IEEE High Performance Extreme Computing Conference (HPEC)}}, publisher = {{IEEE}}, title = {{{Adaptive Spectral Block Floating Point for Discontinuous Galerkin Methods}}}, doi = {{10.1109/hpec67600.2025.11196195}}, year = {{2025}}, } @inproceedings{58861, author = {{Luchterhandt, Lars and Govindasamy, Vivek and Wang, Yutong and Dömer, Rainer and Müller, Wolfgang and Scheytt, J. Christoph}}, booktitle = {{OSSMPIC - Open Source Solutions for Massively Parallel Integrated Circuits}}, title = {{{Case Study on Combining Open-Source Tool Flows for Grids of Processing Cells}}}, year = {{2025}}, } @inproceedings{61079, abstract = {{We propose a spatio-spectral, combined model-based and data-driven diarization pipeline consisting of TDOA-based segmentation followed by embedding-based clustering. The proposed system requires neither access to multi-channel training data nor prior knowledge about the number or placement of microphones. It works for both a compact microphone array and distributed microphones, with minor adjustments. Due to its superior handling of overlapping speech during segmentation, the proposed pipeline significantly outperforms the single-channel pyannote approach, both in a scenario with a compact microphone array and in a setup with distributed microphones. Additionally, we show that, unlike fully spatial diarization pipelines, the proposed system can correctly track speakers when they change positions.}}, author = {{Cord-Landwehr, Tobias and Gburrek, Tobias and Deegen, Marc and Haeb-Umbach, Reinhold}}, booktitle = {{Proceedings of INTERSPEECH}}, location = {{Rotterdam}}, title = {{{Spatio-spectral diarization of meetings by combining TDOA-based segmentation and speaker embedding-based clustering}}}, doi = {{10.21437/Interspeech.2025-1663}}, year = {{2025}}, } @inproceedings{58856, author = {{Hannemann, Kai Arne and Bütün, Hüseyin Berke and Müller, Wolfgang and Scheytt, J. Christoph}}, booktitle = {{MBMV 2025 - 28. Workshop Methoden und Beschreibungssprachen zur Modellierung und Verifikation von Schaltungen und Systemen}}, isbn = {{978-3-8007-6515-7}}, publisher = {{VDE Verlag}}, title = {{{Verilator and FireSim RTL Simulations on a HPC Cluster: A Comparative Case Study}}}, year = {{2025}}, } @inproceedings{62301, author = {{Dreiling, Dmitrij and Itner, Dominik and Gravenkamp, Hauke and Birk, Carolin and Henning, Bernd}}, booktitle = {{2025 International Congress on Ultrasonics}}, pages = {{102–105}}, publisher = {{AMA Service GmbH}}, title = {{{A Measurement Setup for the Determination of Temperature-Dependent Viscoelastic Material Parameters Using an Ultrasonic Pulse-Echo Technique}}}, doi = {{10.5162/ultrasonic2025/a12-c5}}, year = {{2025}}, } @article{62862, abstract = {{Exciton polariton condensates are macroscopic coherent states in which topological excitations can be observed. In this work, we observe the excitation of the vortices and realize tuning the topological charge by manipulating the pumping configurations. Using a digital micromirror device, we constructed an annular pumping pattern where the inner and outer rings can be easily tuned. Both the number and the topological charge of the vortices can be changed by slightly tuning the inner ring position against the outer ring. The experimental results can be reproduced in theory by the Gross–Pitaevskii equation. Our work offers to generate and manipulate vortices in exciton polariton condensates using a straightforward optical method.}}, author = {{Ai, Qiang and Ma, Xuekai and Barkhausen, Franziska and Zhai, Xiaokun and Xing, Chunzi and Yang, Xinmiao and Wang, Peilin and Liu, Tianyu and Zhang, Yong and Gu, Yazhou and Li, Peigang and Li, Zhitong and Hatzopoulos, Zacharias and Savvidis, Pavlos G. and Schumacher, Stefan and Gao, Tingge}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, number = {{12}}, publisher = {{AIP Publishing}}, title = {{{Tuning polariton vortices in an asymmetric ring potential}}}, doi = {{10.1063/5.0287076}}, volume = {{127}}, 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{60992, abstract = {{Non-Hermitian systems hosting exceptional points (EPs) exhibit enhanced sensitivity and unconventional mode dynamics. Going beyond isolated EPs, here we report on the existence of exceptional rings (ERs) in planar optical resonators with specific form of circular dichroism and TE-TM splitting. Such exceptional rings possess intriguing topologies as discussed earlier for condensed matter systems, but they remain virtually unexplored in presence of nonlinearity, for which our photonic platform is ideal. We find that when Kerr-type nonlinearity (or saturable gain) is introduced, the linear ER splits into two concentric ERs, with the larger-radius ring being a ring of third-order EPs. Transitioning from linear to nonlinear regime, we present a rigorous analysis of spectral topology and report enhanced and adjustable perturbation response in the nonlinear regime. Whereas certain features are specific to our system, the results on non-Hermitian spectral topology and nonlinearity-enhanced perturbation response are generic and equally relevant to a broad class of other nonlinear non-Hermitian systems, providing a universal framework for engineering ERs and EPs in nonlinear non-Hermitian systems.}}, author = {{Wingenbach, Jan and Ares Santos, Laura and Ma, Xuekai and Sperling, Jan and Schumacher, Stefan}}, journal = {{Arxiv}}, publisher = {{Arxiv}}, title = {{{Sensitivity and Topology of Exceptional Rings in Nonlinear Non-Hermitian Planar Optical Microcavities}}}, doi = {{10.48550/ARXIV.2507.07099}}, year = {{2025}}, } @article{62926, abstract = {{Abstract Negatively charged boron vacancies () in hexagonal boron nitride (hBN) are emerging as promising solid‐state spin qubits due to their optical accessibility, structural simplicity, and compatibility with photonic platforms. However, quantifying the density of such defects in thin hBN flakes has remained elusive, limiting progress in device integration and reproducibility. Here, an all‐optical method is presented to quantify defect density in hBN by correlating Raman and photoluminescence (PL) signatures with irradiation fluence. Two defect‐induced Raman modes, D1 and D2, are identified and assigned them to vibrational modes of using polarization‐resolved Raman measurements and density functional theory (DFT) calculations. By adapting a numerical model originally developed for graphene, an empirical relationship linking Raman (D1, E 2g ) and PL intensities is established to absolute defect densities. This method is universally applicable across various irradiation types and uniquely suited for thin flakes, where conventional techniques fail. The approach enables accurate, direct, and non‐destructive quantification of spin defect densities down to 10 15  defects/cm 3 , offering a powerful tool for optimizing and benchmarking hBN for quantum optical applications. }}, author = {{Patra, Atanu and Konrad, Paul and Sperlich, Andreas and Biktagirov, Timur and Schmidt, Wolf Gero and Spencer, Lesley and Aharonovich, Igor and Höfling, Sven and Dyakonov, Vladimir}}, issn = {{1616-301X}}, journal = {{Advanced Functional Materials}}, publisher = {{Wiley}}, title = {{{Quantifying Spin Defect Density in hBN via Raman and Photoluminescence Analysis}}}, doi = {{10.1002/adfm.202517851}}, year = {{2025}}, } @article{60913, abstract = {{ABSTRACTSpin‐coated polylactide (PLA) thin films were exposed to nitrogen plasma for varying time intervals. The progressive etching of the PLA film in direct contact with the nitrogen plasma was monitored in situ using polarization modulated infrared reflection absorption spectroscopy (PM‐IRRAS). No appreciative changes in composition were seen with PM‐IRRAS, indicating that the etching did not significantly affect the bulk composition. Atomic force microscopy characterization of the plasma‐etched films showed that the PLA films are homogeneously etched. Subsequent ex situ XPS analysis of the treated surface revealed the presence of C‐N bonds in the surface‐near region that could be associated with amino and/or amide surface species. PLA films were also alternatively exposed to nitrogen ion beams produced by an electron‐cyclotron‐resonance (ECR) plasma source and were investigated in vacuo by XPS. This treatment revealed the partial substitution of surface oxygen species by nitrogen, resulting in a similar surface modification as in the plasma case. The comparison of XPS data and water contact angle studies suggest that the activated surfaces show a reorientation of macromolecular fragments in the surface‐near region depending on the polarity of the phase with which they are in contact. Under ultra‐high vacuum (UHV) conditions, the surface tends to lower its surface energy, while in contact with the aqueous phase, subsurface polar groups orientate outwards, which enables the formation of hydrogen bonds.}}, author = {{Golebiowska, Sandra Alicja and Voigt, Markus and de los Arcos, Teresa and Grundmeier, Guido}}, issn = {{0142-2421}}, journal = {{Surface and Interface Analysis}}, number = {{7}}, pages = {{499--509}}, publisher = {{Wiley}}, title = {{{In Situ PM‐IRRAS and XPS Analysis of Nitrogen Plasma Surface Modification of Polylactide Thin Films}}}, doi = {{10.1002/sia.7406}}, volume = {{57}}, year = {{2025}}, } @article{62936, author = {{Ruhm, Lukas and Neßlinger, Vanessa and Becker, Roman and Meschut, Gerson and Grundmeier, Guido}}, issn = {{0143-7496}}, journal = {{International Journal of Adhesion and Adhesives}}, publisher = {{Elsevier BV}}, title = {{{A contribution to the mechanistic understanding of the improvement of the delamination resistance of adhesives on steel by grit-blasting}}}, doi = {{10.1016/j.ijadhadh.2025.104147}}, volume = {{143}}, year = {{2025}}, } @article{62938, author = {{Müller, Hendrik and Cetin, Ali and Dahlmann, Rainer and de los Arcos, Teresa and Grundmeier, Guido}}, issn = {{0257-8972}}, journal = {{Surface and Coatings Technology}}, publisher = {{Elsevier BV}}, title = {{{Interface chemistry and adhesion of thin bilayer Si-organic PECVD barrier films on post-consumer recycled polypropylene}}}, doi = {{10.1016/j.surfcoat.2025.132392}}, volume = {{512}}, year = {{2025}}, } @article{62939, author = {{Su, Jiangling and Muhle, Marius and Nembot, Nelly and Prüßner, Tim and Xie, Xiaofan and Wittstock, Gunther and Grundmeier, Guido}}, issn = {{0013-4686}}, journal = {{Electrochimica Acta}}, publisher = {{Elsevier BV}}, title = {{{Spontaneous grafting of nitrobenzenediazonium salt on plasma-modified copper substrates}}}, doi = {{10.1016/j.electacta.2025.147810}}, volume = {{546}}, year = {{2025}}, }