@article{61359, abstract = {{AbstractThe current efficiency records for generating green hydrogen via solar water splitting are held by indium phosphide (InP)‐based photo‐absorbers, protected by TiO2 layers grown through atomic layer deposition (ALD). InP is also a leading material for photonic integrated circuits and computing, where ultrafast near‐surface behavior is key. A previous study described electronic pathways at the phosphorus‐rich (P‐rich) surface of p‐doped InP(100) using time‐resolved two‐photon photoemission (tr‐2PPE) spectroscopy. Here, the intricate electron pathways of the P‐rich InP surface modified with ALD‐deposited TiO2 are explored. Photoexcited bulk InP electrons migrate through a bulk‐to‐surface transition cluster of states and surface states and inject into the TiO2 conduction band (CB). Energy levels and occupation dynamics of CB states in P‐rich InP and TiO2 adlayers are observed, with discrete states preserved up to 10 nm TiO2 deposition. Thermalization lifetimes of excited electrons > 0.8 eV above the InP conduction band minimum (CBM) are preserved for layer thicknesses up to 2.5 nm. Annealing at 300 °C to achieve crystalline TiO2 reconstructions destroys interfacial states, affecting charge transfer. These observations enable innovative engineering of the P‐rich InP/TiO2 heterointerface, opening new possibilities for studying hot‐carrier extraction, adsorbate effects, surface plasmons, and improving photovoltaic and PEC water‐splitting devices.}}, author = {{Diederich, Jonathan and Rojas, Jennifer Velazquez and Paszuk, Agnieszka and Pour, Mohammad Amin Zare and Höhn, Christian and Alvarado, Isaac Azahel Ruiz 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 = {{1616-301X}}, journal = {{Advanced Functional Materials}}, number = {{49}}, publisher = {{Wiley}}, title = {{{Ultrafast Electron Dynamics at the P‐rich Indium Phosphide/TiO2 Interface}}}, doi = {{10.1002/adfm.202409455}}, volume = {{34}}, year = {{2024}}, } @article{60581, abstract = {{Abstract The natural band alignments between indium phosphide and the main dioxides of titanium, i.e. rutile, anatase, and brookite as well as amorphous titania are calculated from the branch-point energies of the respective materials. Irrespective of the titania polymorph considered, type-I band alignment is predicted. This may change, however, in dependence on the microscopic interface structure: supercell calculations for amorphous titania grown on P-rich InP(001) surfaces result in a titania conduction band that nearly aligns with that of InP. Depending on the interface specifics, both type-I band and type-II band alignments are observed in the simulations. This agrees with recent experimental findings.}}, author = {{Ruiz Alvarado, Isaac Azahel and Dreßler, Christian and Schmidt, Wolf Gero}}, issn = {{0953-8984}}, journal = {{Journal of Physics: Condensed Matter}}, number = {{7}}, publisher = {{IOP Publishing}}, title = {{{Band alignment at InP/TiO2 interfaces from density-functional theory}}}, doi = {{10.1088/1361-648x/ad9725}}, volume = {{37}}, year = {{2024}}, } @article{54867, abstract = {{ Artificial leaves could be the breakthrough technology to overcome the limitations of storage and mobility through the synthesis of chemical fuels from sunlight, which will be an essential component of a sustainable future energy system. However, the realization of efficient solar‐driven artificial leaf structures requires integrated specialized materials such as semiconductor absorbers, catalysts, interfacial passivation, and contact layers. To date, no competitive system has emerged due to a lack of scientific understanding, knowledge‐based design rules, and scalable engineering strategies. Herein, competitive artificial leaf devices for water splitting, focusing on multiabsorber structures to achieve solar‐to‐hydrogen conversion efficiencies exceeding 15%, are discussed. A key challenge is integrating photovoltaic and electrochemical functionalities in a single device. Additionally, optimal electrocatalysts for intermittent operation at photocurrent densities of 10–20 mA cm−2 must be immobilized on the absorbers with specifically designed interfacial passivation and contact layers, so‐called buried junctions. This minimizes voltage and current losses and prevents corrosive side reactions. Key challenges include understanding elementary steps, identifying suitable materials, and developing synthesis and processing techniques for all integrated components. This is crucial for efficient, robust, and scalable devices. Herein, corresponding research efforts to produce green hydrogen with unassisted solar‐driven (photo‐)electrochemical devices are discussed and reported.}}, author = {{Hannappel, Thomas and Shekarabi, Sahar and Jaegermann, Wolfram and Runge, Erich and Hofmann, Jan Philipp and van de Krol, Roel and May, Matthias M. and Paszuk, Agnieszka and Hess, Franziska and Bergmann, Arno and Bund, Andreas and Cierpka, Christian and Dreßler, Christian and Dionigi, Fabio and Friedrich, Dennis and Favaro, Marco and Krischok, Stefan and Kurniawan, Mario and Lüdge, Kathy and Lei, Yong and Roldán Cuenya, Beatriz and Schaaf, Peter and Schmidt‐Grund, Rüdiger and Schmidt, Wolf Gero and Strasser, Peter and Unger, Eva and Vasquez Montoya, Manuel F. and Wang, Dong and Zhang, Hongbin}}, issn = {{2367-198X}}, journal = {{Solar RRL}}, number = {{11}}, publisher = {{Wiley}}, title = {{{Integration of Multijunction Absorbers and Catalysts for Efficient Solar‐Driven Artificial Leaf Structures: A Physical and Materials Science Perspective}}}, doi = {{10.1002/solr.202301047}}, volume = {{8}}, 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{60582, abstract = {{AbstractThe current efficiency records for generating green hydrogen via solar water splitting are held by indium phosphide (InP)‐based photo‐absorbers, protected by TiO2 layers grown through atomic layer deposition (ALD). InP is also a leading material for photonic integrated circuits and computing, where ultrafast near‐surface behavior is key. A previous study described electronic pathways at the phosphorus‐rich (P‐rich) surface of p‐doped InP(100) using time‐resolved two‐photon photoemission (tr‐2PPE) spectroscopy. Here, the intricate electron pathways of the P‐rich InP surface modified with ALD‐deposited TiO2 are explored. Photoexcited bulk InP electrons migrate through a bulk‐to‐surface transition cluster of states and surface states and inject into the TiO2 conduction band (CB). Energy levels and occupation dynamics of CB states in P‐rich InP and TiO2 adlayers are observed, with discrete states preserved up to 10 nm TiO2 deposition. Thermalization lifetimes of excited electrons > 0.8 eV above the InP conduction band minimum (CBM) are preserved for layer thicknesses up to 2.5 nm. Annealing at 300 °C to achieve crystalline TiO2 reconstructions destroys interfacial states, affecting charge transfer. These observations enable innovative engineering of the P‐rich InP/TiO2 heterointerface, opening new possibilities for studying hot‐carrier extraction, adsorbate effects, surface plasmons, and improving photovoltaic and PEC water‐splitting devices.}}, author = {{Diederich, Jonathan and Rojas, Jennifer Velazquez and Paszuk, Agnieszka and Pour, Mohammad Amin Zare and Höhn, Christian and Ruiz Alvarado, Isaac Azahel 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 = {{1616-301X}}, journal = {{Advanced Functional Materials}}, number = {{49}}, publisher = {{Wiley}}, title = {{{Ultrafast Electron Dynamics at the P‐rich Indium Phosphide/TiO2 Interface}}}, doi = {{10.1002/adfm.202409455}}, volume = {{34}}, 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{62853, abstract = {{Abstract Developing coherent excitation methods for quantum emitters ensuring high brightness, optimal single‐photon purity and indistinguishability of the emitted photons has been a key challenge in the past years. While various methods have been proposed and explored, they all have specific advantages and disadvantages. This study investigates the dynamics of the recent swing‐up scheme as an excitation method for a two‐level system and its performance in single‐photon generation. By applying two far red‐detuned laser pulses, the two‐level system can be prepared in the excited state with near‐unity fidelity. The successful operation and coherent character of this technique are demonstrated using a semiconductor quantum dot (QD). Moreover, the multi‐dimensional parameter space of the two laser pulses is explored to analyze its impact on excitation fidelity. Finally, the performance of the scheme as an excitation method for generating high‐quality single photons is analyzed. The swing‐up scheme itself proves effective, exhibiting nearly perfect single‐photon purity, while the observed indistinguishability in the studied sample is limited by the influence of the inevitable high excitation powers on the semiconductor environment of the quantum dot.}}, author = {{Boos, Katarina and Sbresny, Friedrich and Kim, Sang Kyu and Kremser, Malte and Riedl, Hubert and Bopp, Frederik W. and Rauhaus, William and Scaparra, Bianca and Jöns, Klaus and Finley, Jonathan J. and Müller, Kai and Hanschke, Lukas}}, issn = {{2511-9044}}, journal = {{Advanced Quantum Technologies}}, number = {{4}}, publisher = {{Wiley}}, title = {{{Coherent Swing‐Up Excitation for Semiconductor Quantum Dots}}}, doi = {{10.1002/qute.202300359}}, volume = {{7}}, year = {{2024}}, } @unpublished{62858, abstract = {{Phonons in solid-state quantum emitters play a crucial role in their performance as photon sources in quantum technology. For resonant driving, phonons dampen the Rabi oscillations resulting in reduced preparation fidelities. The phonon spectral density, which quantifies the strength of the carrier-phonon interaction, is non-monotonous as a function of energy. As one of the most prominent consequences, this leads to the reappearance of Rabi rotations for increasing pulse power, which was theoretically predicted in Phys. Rev. Lett. 98, 227403 (2007). In this paper we present the experimental demonstration of the reappearance of Rabi rotations.}}, author = {{Hanschke, L. and Bracht, T. K. and Schöll, E. and Bauch, David and Berger, Eva and Kallert, Patricia and Peter, M. and Garcia, A. J. and Silva, S. F. Covre da and Manna, S. and Rastelli, A. and Schumacher, Stefan and Reiter, D. E. and Jöns, Klaus}}, booktitle = {{arXiv:2409.19167}}, title = {{{Experimental measurement of the reappearance of Rabi rotations in semiconductor quantum dots}}}, year = {{2024}}, } @unpublished{62856, abstract = {{On-chip emitters that can generate single and entangled photons are essential building blocks for developing photonic quantum information processing technologies in a scalable fashion. Semiconductor quantum dots (QDs) are attractive candidates that emit high-quality quantum states of light on demand, however at a rate limited by their spontaneous radiative lifetime. In this study, we utilize the Purcell effect to demonstrate up to a 38-fold enhancement in the emission rate of InAs QDs by coupling them to metal-clad GaAs nanopillars. These cavities, featuring a sub-wavelength mode volume of 4.5x10-4 (λ/n)3 and low quality factor of 62, enable Purcell-enhanced single-photon emission across a large bandwidth of 15 nm. The broadband nature of the cavity eliminates the need for implementing tuning mechanisms typically required to achieve QD-cavity resonance, thus relaxing fabrication constraints. Ultimately, this QD-cavity architecture represents a significant stride towards developing solid-state quantum emitters generating near-ideal single-photon states at GHz-level repetition rates.}}, author = {{Jöns, Klaus}}, title = {{{Purcell-enhanced single-photon emission from InAs/GaAs quantum dots coupled to broadband cylindrical nanocavities}}}, year = {{2024}}, } @inbook{56162, abstract = {{Die Autorinnen untersuchen im Rahmen ihrer Prä-Post-Studie mit Viertklässlern, ob der Modellierungsprozess durch analoges Schließen zwischen mehreren Phänomenen unterstützt werden kann, und ob chemische Konzepte zum Thema Löslichkeit erlernt werden können. Die Ergebnisse zeigen, dass Grundschüler*innen ihre mentalen Modelle in einem Modell ausdrücken und teilweise revidieren können. In einigen Fällen werden die Modelle reflektiert und Grenzen erkannt. (DIPF/Orig.)}}, author = {{Elsner, Julia and Tenberge, Claudia and Fechner, Sabine}}, booktitle = {{In Alternativen denken - Kritik, Reflexion und Transformation im Sachunterricht}}, editor = {{Egger, Christina and Neureiter, Herbert and Peschel, Markus and Goll, Thomas}}, isbn = {{9783781526235}}, pages = {{83--92}}, publisher = {{Verlag Julius Klinkhardt}}, title = {{{Analyse des Modellierprozesses von Grundschüler*innen zum Thema Löslichkeit}}}, doi = {{10.35468/6077-08}}, year = {{2024}}, } @article{63048, title = {{{High-throughput antibody screening with high-quality factor nanophotonics and bioprinting}}}, doi = {{10.48550/ARXIV.2411.18557}}, year = {{2024}}, } @misc{63047, author = {{Güsken, Nicholas Alexander}}, title = {{{Schottky-barrier type infrared photodetector }}}, year = {{2024}}, } @article{63044, author = {{Hoessbacher, C. and Baeuerle, B. and Del Medico, N. and De Leo, E. and Güsken, Nicholas Alexander and Heni, W. and Langenbach, A. and Tedaldi, V.}}, issn = {{2732-4494}}, journal = {{IET Conference Proceedings}}, number = {{34}}, pages = {{1606--1608}}, publisher = {{Institution of Engineering and Technology (IET)}}, title = {{{Plasmonic modulators: bringing a new light to silicon}}}, doi = {{10.1049/icp.2023.2642}}, volume = {{2023}}, year = {{2024}}, } @article{63049, author = {{Güsken, Nicholas Alexander and Brongersma, Mark L.}}, issn = {{2791-1748}}, journal = {{Photonics Insights}}, number = {{4}}, publisher = {{Shanghai Institute of Optics and Fine Mechanics}}, title = {{{Electrifying the field of metasurface optics}}}, doi = {{10.3788/pi.2024.c08}}, volume = {{3}}, year = {{2024}}, } @article{53202, abstract = {{At large scales, quantum systems may become advantageous over their classical counterparts at performing certain tasks. Developing tools to analyze these systems at the relevant scales, in a manner consistent with quantum mechanics, is therefore critical to benchmarking performance and characterizing their operation. While classical computational approaches cannot perform like-for-like computations of quantum systems beyond a certain scale, classical high-performance computing (HPC) may nevertheless be useful for precisely these characterization and certification tasks. By developing open-source customized algorithms using high-performance computing, we perform quantum tomography on a megascale quantum photonic detector covering a Hilbert space of 106. This requires finding 108 elements of the matrix corresponding to the positive operator valued measure (POVM), the quantum description of the detector, and is achieved in minutes of computation time. Moreover, by exploiting the structure of the problem, we achieve highly efficient parallel scaling, paving the way for quantum objects up to a system size of 1012 elements to be reconstructed using this method. In general, this shows that a consistent quantum mechanical description of quantum phenomena is applicable at everyday scales. More concretely, this enables the reconstruction of large-scale quantum sources, processes and detectors used in computation and sampling tasks, which may be necessary to prove their nonclassical character or quantum computational advantage.}}, author = {{Schapeler, Timon and Schade, Robert and Lass, Michael and Plessl, Christian and Bartley, Tim}}, journal = {{Quantum Science and Technology}}, number = {{1}}, publisher = {{IOP Publishing}}, title = {{{Scalable quantum detector tomography by high-performance computing}}}, doi = {{10.1088/2058-9565/ad8511}}, volume = {{10}}, year = {{2024}}, }