NEWS
18.07.2024Prof. Nicola Pinna pioneered a novel technique for coating nano-particles and creates yolk-shell nanostructures.Prof. Pinna, member of IRIS Adlershof, and colleagues have revolutionized the Stöber method, originally for amorphous SiO2 colloids, by extending it to metal-organic frameworks (MOFs) and coordination polymers (CPs). Their innovative approach harnesses the slow, continuous diffusion of triethylamine (TEA) vapor to precisely control the deprotonation of organic ligands, paving the way for creating finely crafted amorphous CP spheres. 03.07.2024DFG bewilligt neue Forschungsgruppe MFOSA im Bereich der Quantenfeldtheorie
Eine Gruppe führender theoretischer Physiker*innen hat sich zusammengeschlossen, um die Grundlagen von Streuamplituden - fundamentalen Größen in der Quantenfeldtheorie - zu erforschen. Die Deutsche Forschungsgemeinschaft (DFG) fördert diese neue Forschungsgruppe unter der Leitung von Prof. Dr. Claude Duhr von der Universität Bonn für vier Jahre mit einer Summe von etwa 4 Millionen Euro. Maßgeblich beteiligt sind auch Forschende des IRIS Adlershof (HU): Prof. Dr. Valentina Forini und Prof. Dr. Jan Plefka, die ihre Expertise in den Bereichen Quantenfeldtheorie, Stringtheorie und Gravitationsphysik einbringen. Streuamplituden beschreiben die Wechselwirkungen zwischen Elementarteilchen und sind von zentraler Bedeutung für unser Verständnis der fundamentalen Naturkräfte – der elektromagnetischen, der starken und schwachen Kernkraft, sowie der Gravitation. Die Forschungsgruppe wird innovative Methoden entwickeln, um diese komplexen mathematischen Objekte zu berechnen und ihre zugrundeliegende Struktur zu entschlüsseln. Zu den Hauptzielen gehören:
Prof. Plefka wird insbesondere seine Arbeit zu Weltlinien-Quantenfeldtheorien einbringen, die innovative Ansätze für die Gravitationswellenphysik liefert. Prof. Forini wird ihre Expertise in der Anwendung von Unitaritätstechniken auf gekrümmte Raumzeiten, insbesondere Anti-de-Sitter-Räume, beisteuern. Die Forschungsgruppe vereint Expertinnen und Experten aus verschiedenen Bereichen der theoretischen und mathematischen Physik von sechs führenden deutschen Forschungseinrichtungen sowie der University of Hertfordshire (UK). Durch die enge Zusammenarbeit und den Austausch von Ideen sollen bahnbrechende Fortschritte in diesem wichtigen Forschungsgebiet erzielt werden. Die gewonnenen Erkenntnisse werden nicht nur das fundamentale Verständnis der Naturgesetze erweitern, sondern auch direkte Anwendungen in der Teilchen- und Gravitationsphysik ermöglichen. Dies betrifft zum einen hochpräzise Vorhersagen für den Ausgang von Streuprozessen am Large Hadron Collider am CERN in Genf, sowie die Berechnung der Gravitationswellenformen aus Begegnungen von schwarzen Löchern und Neutronensternen in unserem Universum, die in modernen Gravitationswellendetektoren gemessen werden. Kontakt:
20.06.2024Dr. Gustav Mogull Receives the Karl Scheel Prize from the Physical Society of Berlin 2024
Dr. Gustav Mogull, a young researcher at the Department of Physics at Humboldt-Universität zu Berlin and associated with the Max Planck Institute for Gravitational Physics (Albert Einstein Institute), is receiving the prestigious Karl Scheel Prize for his groundbreaking work in the field of general relativity and gravitational wave physics. Since the first observation of gravitational waves in 2015, a new field of research has emerged to study black holes, neutron stars, and test general relativity in extreme gravitational fields. Dr. Mogull has created a novel theoretical framework called the Worldline Quantum Field Theory (WQFT), developed in the research group of IRIS Adlershof-member Prof. Dr. Jan Plefka, to compute high-precision analytical predictions for the classical two-body problem in general relativity. Using WQFT, Dr. Mogull has derived important physical observables for the dynamics of black holes and neutron stars in a series of papers published in prestigious journals such as Physical Review Letters. His results are already being applied in modeling gravitational wave signals for data analysis of current and planned future gravitational wave detectors. The prize honors Dr. Mogull's outstanding theoretical work on the two-body problem, which is of great importance for future high-precision tests of general relativity and our understanding of gravitational waves. The crucial advance of WQFT lies in the transfer of methods from quantum field theory, which usually describes elementary particle physics, to the interaction of black holes. In this sense, one replaces the theoretical description of the scattering of protons in particle accelerators with the scattering of black holes in our universe. The Karl Scheel Prize, endowed with 5,000 euros, is awarded annually by the German Physical Society of Berlin for outstanding achievements in physics. Gustav Mogull studied at the University of Cambridge and received his PhD in Edinburgh with work on scattering amplitudes in quantum field theory. After a postdoc in Uppsala (Sweden), he has been a long-term postdoc at the DFG Research Training Group "Rethinking Quantum Field Theory" (Speaker: Prof. Dr. J. Plefka) since 2020, which was recently extended for a second funding phase. The award-winning work was carried out within the framework of this research project, and Mr. Mogull is also actively involved in co-supervising doctoral and master’s thesis students in the program. He has recently received a fellowship from the Royal Society, which will lead him to a lectureship at Queen Mary University London starting in the fall of 2024. Contact: Dr. Mogull and Prof. Dr. Plefka, Department of Physics, GRK 2575. 19.06.2024Breakthrough in Gravitational Wave Physics:
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Dr. Mogull & Visualization of the scattering of two black holes including a wave profile |
| Jan Plefka, member of IRIS Adlershof |
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| Visualization of the scattering of two black holes including a wave profile |
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| Visualization of the gravitational Bremsstrahlung from the scattering of two black holes (BSc thesis O. Babayemi) |
In a groundbreaking achievement, an international team led by IRIS Adlershof member Jan Plefka has computed the dynamics of two black holes scattering off each other at the highest level of precision ever attained. Their work, published as an Editor's Choice in the prestigious journal Physical Review Letters, provides new insights into the powerful gravitational interactions between these extreme objects.
Black hole scattering is a fundamental problem in Einstein's theory of general relativity, with wide-ranging implications for astrophysics and gravitational wave astronomy. Understanding the gravitational interactions and radiation emitted when two black holes encounter each other is crucial for interpreting observations from gravitational wave detectors like LIGO and future third generation wave detectors scheduled to go nonline in the 2030s.
The new calculations, performed by researchers from Humboldt University Berlin, the Max Planck Institute for Gravitational Physics, and CERN, push the theoretical description of black hole scattering to unprecedented accuracy - the fifth post-Minkowskian order and next-to leading self-force order. This enormously challenging four-loop computation required state-of-the-art integration techniques and high-performance computing resources.
"Resolving this problem represents a new frontier in multi-loop calculations and effective field theory techniques," said group leader Jan Plefka. Co-author Benjamin Sauer commented "We had to optimize every aspect, from the integrand generation to developing new integration-by-parts methods." In total millions of 16 dimensional integrals had to be reduced to a basis of 470 master integrals, which were then computed.
Remarkably, the researchers found that at this new level of precision, the resulting scattering angle exhibits striking simplicity, without the appearance of new transcendental functions beyond polylogarithms of weight three. All theoretical checks, both internal and by matching to previous results, were passed successfully.
With this breakthrough, the researchers have laid the groundwork for incorporating their calculations into advanced gravitational waveform models for the next generation of gravitational wave detectors. The higher precision will enable exquisitely accurate tests of Einstein's theory and new insights into nuclear and fundamental physics from binary inspirals.
"Our results bring the prediction of gravitational waves from black hole encounters to unprecedented accuracy," said co-author Gustav Uhre Jakobsen. "This opens brilliant new avenues for extracting fundamental physics from gravitational wave observations in the future."
The research was funded by the Deutsche Forschungsgemeinschaft in the context of the Research Training Group 2575 “Rethinking Quantum Field Theory” and the European Research Council Advanced Grant “GraWFTy” of Jan Plefka.
Article:
Conservative Black Hole Scattering at Fifth Post-Minkowskian and First Self-Force Order
Mathias Driesse, Gustav Uhre Jakobsen, Gustav Mogull, Jan Plefka, Benjamin Sauer, and Johann Usovitsch
Phys. Rev. Lett. 132, 241402 – Published 13 June 2024
DOI: 10.1103/PhysRevLett.132.241402
Contact:
Prof. Dr. Jan Plefka
Sprecher Graduiertenkolleg 2575 „Rethinking Quantum Field Theory“
ERC Advanced Grant „GraWFTy"
Humboldt-Universität zu Berlin, IRIS Adlershof &
Institut für Physik, Arbeitsgruppe Quantenfeld- und Stringtheorie
Zum Großen Windkanal 2, D-12489 Berlin
Postal adress: Unter den Linden 6, 10099 Berlin, Germany
Email: jan.plefkahu-berlin.de
Tel: +49 (0)30 2093 66409
Sekr.: +49 (0)30 2093 66413
qft.physik.hu-berlin.de
www2.hu-berlin.de/rtg2575/
X: @JanPlefka
19.06.2024Enhanced surface-to-bulk Raman signal ratio using a transferable porous gold membrane
Enhanced surface-to-bulk Raman signal ratio using a transferable porous gold membrane
In a recent collaboration of the Emmy Noether Research Group "Physics of low-dimensional systems" around IRIS Adlershof member Dr. Sebastian Heeg at HU Berlin, researchers from the Leibniz-Institut für Kristallzüchtung (IKZ), the Université Le Mans, and the ETH Zurich, realized a novel modality in Raman spectroscopy through the development of surface-sensitive Raman scattering. This new approach addresses a major limitation of conventional Raman spectroscopy, where signals from surfaces or thin films are often weak and obscured by dominant bulk signals.
Surfaces play a pivotal role in science and industry as they are where most environmental interactions occur, including chemical reactions, adhesion, friction, and light interactions. Surface properties may differ significantly from bulk properties in terms of chemical composition, atomic arrangement, and electronic structure, influencing technological advancements such as catalysts and solar cells. Raman spectroscopy, a powerful, non-destructive technique for analysing molecular vibrations, provides insights into a material's chemical composition, crystallinity, defects, and strain. It is particularly valuable for characterising nanomaterials, thin films, and biological samples where precise surface information is essential.
The application of conventional Raman spectroscopy to surfaces and thin films has been constrained by dominant bulk signals. However, using transferable porous gold membranes (PAuMs) allows for the study of surface-specific Raman signals with unprecedented clarity. PAuMs contain irregular, slot-shaped nanopores that act as plasmonic antennas. When placing PAuM on a surface or thin film of interest, the nanopores amplify the Raman signal of the surface directly below while the membrane itself suppresses bulk signals. Combining these effects improves the surface-to-bulk Raman signal ratio by three orders of magnitude and enables truly surface-sensitive Raman scattering.
The researchers used graphene as a model surface, observing that the nanopores in the membranes enhance the graphene Raman signal a hundredfold. Placing a spacer between graphene and the PAuM reveals that the Raman enhancement is confined to the first 2 – 3 nm of the material below the membrane, which demonstrates true surface sensitivity. A first prototypal application regards quantifying the strain in a 12.5 nm thin Si quantum well layer using PAuMs. The layer is part of a Silicon-Germanium heterostructure designed to use spin qubits as a promising and fast-developing technology for quantum computing.
In a second use-case, PAuMs are used to study the surface of thin LaNiO3 film, a metallic perovskite used as an electrode material. The electrical conductivity of LaNiO3 films is strongly coupled to its crystallographic structure and can be tuned by the film thickness. With PAuM placed on top of LaNiO3, the authors observed a Raman mode splitting arising from the film’s surface and indicating a difference in the surface structure compared to the bulk. This finding is consistent with theoretical predictions and observations from scanning tunnelling microscopy studies.
“Our work connects two separate fields” says Heeg, “Conceptually, we extend the field of plasmon-enhanced Raman spectroscopy, which is almost exclusively used to study and sense molecular compounds and nanostructures, to the field of solid states materials like Silicon quantum wells, thin complex oxides films, and related surfaces.” The team is now exploring the potential of the method with partners in Berlin and international collaborators. Dr. Pietro Marabotti, Einstein International Postdoctoral Fellow in Heeg’s group and co-author of the study, remarks that “our approach is not limited to crystalline surfaces, which we use as a showcase, but may also be used to study, for example, biological surfaces or surface-bound chemical reactions.” Researchers interested in the method are invited to get in touch with the team.
Bulk-suppressed and surface-sensitive Raman scattering by transferable plasmonic membranes with irregular slot-shaped nanopores
Roman M. Wyss, Günther Kewes, Pietro Marabotti, Stefan M. Koepfli, Karl-Philipp Schlichting, Markus Parzefall, Eric Bonvin, Martin F. Sarott, Morgan Trassin, Maximilian Oezkent, Chen-Hsun Lu, Kevin-P. Gradwohl, Thomas Perrault, Lala Habibova, Giorgia Marcelli, Marcela Giraldo, Jan Vermant, Lukas Novotny, Martin Frimmer, Mads C. Weber, and Sebastian Heeg
Nat. Commun. 15, 5236 (2024).
DOI: 10.1038/s41467-024-49130-2 OPEN
ACCESS
➔ Article on the paper in ETH News
➔ Article on the paper from Humboldt Innovation
Kontakt:
Dr. Sebastian Heeg
Humboldt-Universität zu Berlin
IRIS Adlershof & Institut für Physik
Tel.: 030 2093-82295
E-Mail: sebastian.heegphysik.hu-berlin.de
Website: https://www.physik.hu-berlin.de/en/pld