Copyright: Prof. Dr. Peter Schmelcher
Funded HH-MIT/BOS Seed Projects
Hybrid long-range quantum molecules
Prof. Dr. Peter Schmelcher (UHH)
Project Partner: Dr. Hossein Sadeghpour (Institute for Theoretical, Atomic, Molecular and Optical Physics(ITAMP) at the Harvard-Smithsonian Center for Astrophysics, Cambridge)
Atoms and molecules represent the building blocks of matter ranging from small clusters to extended materials. Their structure and dynamics is governed by the laws of quantum mechanics. Traditional molecules occurring in nature are of highly balanced character in the sense that the atoms forming the molecules are energetically close to their ground state. This does not hold for the artificial ultra-long-range Rydberg molecules (ULRM) of mesoscopic character.
ULRM can be formed in ultracold samples of trapped ground-state atoms, when the outer electron of one atom is excited by a laser into a Rydberg state. In this case the orbit of the electron can become so large that it starts to collide with neighboring atoms. Counterintuitively, these collisions can lead to a chemical bond between the excited atom and the ground-state atom. The hugely sized electronic cloud of the Rydberg atom acts thereby effectively as a trap for the ground-state atom and equips the molecule with a number of extraordinary properties such as a large bond lengths and extreme sensitivities to external fields.
The main focus of our project is to study the transition from a few-body regime to the deep many-body regime which is governed by formation of Rydberg polarons when more and more perturbing ground-state atoms are located within the electronic Rydberg orbital. Here, the character of a ground-state atom acting as a perturber to the Rydberg electronic wave functions changes to a character where the Rydberg excitation acts as a perturber to a bosonic bath. This novel physical system is distinguished by macroscopic occupation of bound molecular states.
Novel aperiodic nanophotonic devices with functional local symmetries
Prof. Dr. Peter Schmelcher (UHH)
Project partner: Prof. Dr. Luca Dal Negro (Boston University, Photonics Center)
The fundamental role of symmetries in physics is reflected in the theoretical predictions they enable for arbitrarily complex systems, without the need for explicit calculations. For example, spectral properties and selection rules in atoms and molecules, band structures of crystalline media, interference phenomena in wave scattering, as well as more general constants of motion, can often be deduced directly from the mere presence of the corresponding symmetries. Such perfect symmetries of infinitely extended or isolated model systems, however, are an idealization rarely encountered. On the other hand, most composite systems feature symmetries in some part of space and different or no symmetries in other parts. This project investigates the impact of such local symmetries onto photonic metamaterials and nanoparticle clusters with plasmon-polariton responses. In particular, our aim is to theoretically develop and experimentally demonstrate a novel and more powerful approach for the engineering of complex photonic nanostructures and metamaterials beyond the limitations imposed by traditional global symmetry principle. A concrete goal of the collaboration during the seed period is the design of two-dimensional, locally symmetric aperiodic nanoparticle devices supporting bound states in the continuum for symmetry-stabilized multi-mode lasing. This achievement would then serve as a prototype for technological implementation.
The Future of Structural Biology – pursuing a global vision shared by MIT and Hamburg
Prof. Dr. Matthias Wilmanns (EMBL Hamburg; UKE)
Project partners: Joseph (Joey) Davis (MIT), Cathy Drennan (MIT), Amy E Keating (MIT)
Structural biology is presently undergoing an unprecedented transition and expansion, mainly due to new technologies in electron cryo-microscopy and unique properties of X-rays from leading synchrotron and X-ray Free Electron Laser facilities. These new capabilities ideally complement established research infrastructures using synchrotron radiation for applications in structural biology. The Massachusetts Institute of Technology (MIT) in the US and several research organisations in Hamburg (Germany) are leading research sites with ambitious research programs from local universities and other research organizations. Hence, synergistic future cooperation between both sites is logical and obvious. Major aims of an inaugural workshop entitled “The Future of Structural Biology – pursuing a global vision shared by MIT and Hamburg” for planning this joint endeavour will include discussion and definition of opportunities for: (i) potential tools of future collaboration, (ii) common elements of a future research strategy, (iii) future approaches for joint training, information and dissemination, and (iv) to explore joint funding opportunities.
We are aiming to organize a workshop of up to 50 participants from Boston and Hamburg with a track record and research interests in relevant fields. The applicants of this proposal will form the organization committee of the workshop. They will disseminate information about the planned workshop in their home and neighboring research organizations and will be in charge of a required decision making procedures (final workshop agenda, budget distribution, participant selection). The workshop will be goal-oriented and highly interactive, i.e. at least 50% of the time will be reserved for discussions. Themes of the workshop will be:
1. Potential tools of future collaboration
2. Common elements of a future Research Strategy
3. Future approaches for joint Training, Information and Dissemination
4. To explore Joint Funding Opportunities
To achieve these aims efficiently and frame them within a scientific agenda, we have agreed to focus the scientific exchange during the workshop on four topics:
1. Novel opportunities and tools in structural biology: X-ray sources (synchrotron, X-ray free electron laser), electron cryo-microscopy (single particle, electron tomography), and complementary tools (single molecule methods, mass spectrometry, biophysical approaches).
2. 4D structural biology: Opportunities and research highlights for time-resolved experiments.
3. The big data challenge: Connecting different schemes and different scales, challenges arising from superfast experiment detection.
4. Research highlights from partners across the pond: To explore future win/win opportunities for cooperation.
Investigations for a Future Two-Photon Exchange Experiment at DESY
Dr. Uwe Schneekloth (DESY)
Project partners: Douglas Hasell (MIT), Or Hen, Richard Milner (MIT) and Robert Redwine (MIT)
To design therapeutics against dementia using novel structural data on the molecular interface between PrP ͨ and fibril/oligomer ends
Dr. Mohsin Shafiq (UKE)
Project partner: Prof. David A. Harris (Department of Biochemistry, Boston University School of Medicine, USA)
The cellular prion protein (PrP ͨ ) is shown to impart a dual role to the progression of the Alzheimer’s disease (AD); extracellularly shed and cleaved forms of PrP ͨ along the exosomally expressed PrP ͨ are suggested to accelerate the Aβ42 fibril formation by sequestering the Aβ oligomers (Aβo) thereby playing a neuroprotective role, in contrast PrP ͨ on the neuronal surface serves as receptors for Aβo and initiate neurotoxic signaling. Ongoing small angle X-ray scattering (SAXS) study carried out by Glatzel’s (UKE Hamburg) and Svergun’s groups (EMBL Hamburg) collectively, on Aβ fibrillation kinetics in the presence of PrP expressing (WT) and PrP deficient (KO) exosomes shows that the presence of exosomes facilitates the Aβ42 fibrillation process. KO exosomes show a relatively lower Aβ42 binding compared to WT exosomes. Relying on super-resolution microscopy (SRM), and biochemical techniques, Harris’s lab (Boston University School of Medicine) has carried out mechanistic studies on putative Aβ receptor properties of PrP ͨ , and has showed that PrP ͨ , in addition to binding to Aβo, also binds to one of the two ends of polymerizing Aβ fibrils, and blocks the elongation fibril. We hypothesize that a similar determinant is also present on neurotoxic Aβo, allowing cell surface PrP ͨ to bind to them and initiate a pathological signaling cascade.
Here we plan to:
• explore the nature of Aβ interaction to various PrP ͨ mutants using SAXS, and
• to utilize the resultant structural information for designing inhibitors of Aβ- PrP ͨ binding, for blocking toxic signaling
Fabrication and Characterization of Field Emitter Arrays for FEL-like X-ray Sources
Prof. Franz X. Kärtner (DESY)
Project partners: Dr. Phillip Keathley (MIT), Prof. Karl K. Berggren (MIT) and Prof. Luca Dal Negro (BU)
We will fabricate and test infrared-driven field-emitter arrays (FEAs) that can be used as field driven cathodes for electron accelerators and Free-Electron Laser-like sources and continue the development of infrared (2-micron) optical parametric amplifier (OPA) sources capable of generating few-cycle pulses of radiation with high peak field strengths for structured electron beam extraction from the field-emitter arrays.
Slab-based terahertz generation for electron acceleration
Prof. Franz X. Kärtner (DESY)
Project partner: Prof. Keith A. Nelson (MIT)
The Nelson and Kaertner groups will follow up a promising collaborative effort that suggested up to an order of magnitude improvement in THz generation efficiency using 800-nm pump light in lithium niobate (LN). A tilted-pulse-front pumping geometry will be modified by using zero-order reflections from a stairstep echelon structure instead of first-order diffraction from a grating, thereby avoiding separation of the optical frequency components which limits the range over which the optical field is reconstructed inside the LN. In this way a significantly larger volume of LN can be pumped effectively to contribute to THz generation. Additionally, a pumping geometry in which the pump light can be re-used many times for THz generation inside a thin LN slab will be optimized. In this approach the pump light undergoes multiple reflections from the front and back sides of a LN slab, continuing to generate THz output with each traversal of the slab. The THz output field components superpose constructively, yielding significant improvement in THz generation efficiency. The scheme could enable strong-field THz generation even with small (μJ) pump energies since the pump light is re-used many times in the generation process. Large (mJ) pump pulse energy could be split to pump many LN slabs, with the THz outputs organized spatially and temporally for electron acceleration.
Probing the Standard Model with Jet Substructure
Prof. Dr. Gregor Kasieczka (UHH)
Project partners: Dr. Andreas Hinzmann (UHH), Dr. Roman Kogler (UHH), Prof. Phil Harris (MIT), Prof. Jesse Thaler (MIT), Prof. Iain Stewart (MIT)
Heavy particles - such as the top quark or electroweak bosons - with large momenta are abundantly produced at the Large Hadron Collider at CERN and are of large interest for a variety of measurements of the Standard Model and searches for signatures of new physical theories. Because of their large branching fractions, the decays into hadrons are of particular interest but raise a special challenge: At these high energies, the decay products are Lorentz-boosted and result in a collimated spray of particles in the detector that is reconstructed with a single large-radius jet.
The mass of the jet is sensitive to the mass of the initial heavy particle and enables not only the identification of a jet’s origin but also measurements of fundamental masses. Both rely on a well calibrated reconstruction of the jet mass with controlled systematic uncertainties. In contrast to established calibration methods based on jets as single objects, we want to calibrate the jet constituents - i.e. the individual particles measured in the detector - themselves. These pioneering studies will have substantial impact, not only by extending the range of current measurements to larger particle momenta but also by enabling the precise extraction of fundamental masses at large energy scales that have not been explored yet. In addition, a vast amount of searches for new physics rely on a profound understanding and calibration of the jet mass an essential observable in the identification of jets.
New THz-sources for Lab-On-Chip Applications
Prof. Dr. Robert Blick (UHH)
Project partners: Prof. Qin Hu (MIT), Prof. Roberto Paiella (Boston University)
Tera-Hertz frequencies (1–10THz; 4–40meV; 30–300mm) are among the most underdeveloped electromagnetic spectra, even though their potential is huge in imaging and sensing applications. This underdevelopment is primarily due to the lack of coherent and powerful solid-state THz sources, since the THz frequency falls between two other frequency ranges in which conventional semiconductor devices have been well developed. One is the microwave and millimeter-wave frequency range, and the other is the near-infrared and optical frequency range. Semiconductor electronic devices that utilize conduction electrons (such as transistors) are limited by the transit time and parasitic RC time constants to below 1 THz. Conventional semiconductor photonic devices (such as bipolar laser diodes), however, are limited to frequencies higher than those corresponding to the semiconductor energy gap (>10 THz).
The new class of Dirac-materials with its prodigy graphene and now combined van-der-Waals materials, such as multi-layer graphene and combinations with transition metal di-chalcogenides (TMDs), are quantum-mechanical systems, which lend themselves perfectly to precisely engineer THz-emitters and detectors. Apart from functioning as plasmonic and optical emitters, modulated graphene layers have a large potential as THz-sources and -receivers. Based on the Smith-Purcell effect we propose to design and fabricate an enhanced, tunable THz-emitter relying on high-mobility two-dimensional carrier system in mechanically-modulated graphene. Such a grating or wiggler – as they are called for large-scale Free Electron Lasers (FELs) – can by now be fabricated down to the scale of several 10nm periodicity. Realizing these novel THz-sources has a huge potential, since they are wideband tunable, scalable, and well suited for integration. They also potentially can be engineered as lasing devices for the THz-range, similar to the quantum cascade laser (QCL). Realizing such compact THz-sources will have a large range of applications for Lab-on-Chip (LOC) devices.
High-Precision Analysis of Transverse- Momentum Distributions at the LHC
Dr. Frank Tackmann, DESY
Project partners: Prof. Iain Stewart (Center of Theoretical Physics, MIT), Dr. Markus Ebert (Center of Theoretical Physics, MIT)
Transverse-momentum, qT , distributions are key benchmark observables at the LHC. The qT spectrum of Z bosons is among the most precisely measured cross sections at the LHC, while the qT spectrum of W and Higgs bosons plays an integral part in the measurement of the W mass and of the properties of the Higgs boson, both of which are high-profile targets of the LHC physics program. The project aims to improve our current understanding of qT distributions by performing detailed theoretical analyses and comparison with the experimental data. One important aspect is to improve the treatment of nonperturbative contributions by developing a field-theoretic treatment for them and by incorporating results from lattice-QCD calculations following a new method recently developed by the participating MIT researchers. Another key element is to improve our understanding of perturbative power corrections and study their resummation, which is currently unknown. In order to directly fit the theoretical predictions to the experimental data, a fast and reliable numerical evaluation of the theoretical predictions is essential. For this purpose, a fast C++ library, SCETlib, has been developed at DESY. The goal of the project is to combine the complementary expertise of the DESY and MIT partners in these different areas to obtain the best possible theoretical description of qT distributions at the LHC going significantly beyond the current state-of-the-art.