The study of coupling between electron-phonon is of fundamental importance to understand Perovskites with interesting photoelectric properties, to address the problem related to the transport properties of materials and to contribute to the debate on the role of electron-phonon coupling in high critical temperature superconductors. Here we present a new approach to detecting the strength of...
Hypergraph states form an interesting family of multi-qubit
quantum states which are useful for quantum error correction,
non-locality and measurement-based quantum computing. They are
a generalisation of graph and cluster states. The states can be
represented by hypergraphs, where the vertices and hyperedges
represent qubits and entangling gates, respectively.
For quantum information...
The KATRIN experiment aims to measure the neutrino mass by precision spectroscopy of tritium β-decay. Recently, KATRIN has improved the upper bound on the effective electron-neutrino mass to 0.8 eV/c² at 90% confidence level [1] and is continuing to take data for a target sensitivity of 0.2 eV/c².
In addition to the search for the neutrino mass, the ultra-precise measurement of the β-spectrum...
The MESA accelerator will host the MAGIX experiment, which is based on the
scattering of an electron beam on a gas jet target. This enables the scattering on gases like hydrogen without scattering on any other materials before and after the scattering process. The gas jet target is realized by using a nozzle to inject the gas into the scattering chamber as well as a funnel-shaped structure...
Quantum dots (QDs) are semiconducting nanoparticles important due to their size-tunable
excitation energy and other optical properties. Self-assembled (SA) QDs are one of the most
promising building blocks for future quantum information processing, as they can host optical,
electronic, or spin qubit states with a decent lifetime1,2.
Qubit switching itself is a dynamical process which is, e.g.,...
Photosynthesis is the basic process of life as we know it. Despite numerous studies, the details of the natural process are still not elucidated. One of the central problems remains the investigation of the CaMn4O5 cluster, which is a main active part of enzyme Photosystem II (PS II) due to its oxygen-evolving functions [1]. A consistent understanding of the electronic and geometric state of...
Clouds play an important role for the composition of the atmosphere and radiation balance. The influences between clouds and atmospheric processes are numerous and complex which makes them hard to quantify. Especially the presence of different aerosols has a strong impact on cloud formation because aerosols are acting as nuclei for cloud droplets and ice crystals.
Volcanic eruptions lead to a...
Photonic quantum devices based on atomic vapors at room temperature are intrinsically reproducible, scalable and integrable. Besides quantum memories for single photons, one key device in the field of quantum information processing are on-demand single-photon sources. A promising candidate for their realization relies on the combination of four-wave mixing and the Rydberg blockade effect. This...
Current pulse-driven Neel vector rotation in metallic antiferromagnets is one of the most promising concepts in antiferromagnetic spintronics. We show microscopically that the Neel vector of epitaxial thin films of the prototypical compound Mn2Au can be reoriented reversibly in the complete area of cross-shaped device structures using single current pulses. The resulting domain pattern...
The theoretical aspect of the four-wave mixing for a four-level diamond scheme in 87Rb atoms will be discussed. Also, the experimental realization of this study will be presented. In this realization, 87Rb are cooled and further trapped in the vicinity of a nanofiber-based waveguide using a two-color evanescent dipole trap scheme. Then, the four-wave mixing is applied on the trapped atoms in...
Lightsheet fluorescence microscopy (LSFM) is currently one of the most efficient types of optical microscopy exposing the sample to a minimal photon dose. In LSFM, the sample is illuminated by an extremely thin "sheet" of light along the focal plane from which fluorescence is detected, such that only those areas of the sample from which fluorescence is detected are exposed. In the majority of...
In order to resolve the internal structure of extended biological samples, i.e. entire organisms, organs, or tissue sections, by optical microscopy, these samples require optical clearing in order to become optically transparent. Optical clearing typically involves a harsh chemical treatment process, where samples are first fixed by chemical crosslinking, lipids are removed by transfer from...
The KATRIN experiment at the Karlsruhe Institute of Technology (KIT) aims at the direct measurement of the electron neutrino mass with 0.2eV/c² sensitivity. The high luminosity windowless gaseous molecular tritium source together with the magnetic adiabatic collimation of the electrostatic (MAC-E) filter technique allows for precision endpoint spectroscopy of the tritium beta decay. The...
An important contribution to the success of micro- and nanotechnologies was and is the possibility of being able to visualize and measure objects on this scale. The calibration of 3D-microscopes today requires not only the calibration of the side and height scales, but also the calibration of the flatness error of coordinate planes as well as the shear of coordinate axes. To meet these...
Ion traps are promising candidates towards scalable quantum computer. One of the possible designs is the multilayer surface electrode ion traps[1]. The different processes involved in realising it are UV photolithography, Electroplating , Reactive Ion etching and more. Research and development towards the scalable quantum computer is tried with TSVs (through substrate vias) and Flip Chip...
In transition metal-oxygen species, the way the oxygen atoms are bonded to the metal center is found to play a significant role in their reactivity, in view of different types of oxygen ligands and unusual oxidation states.$^{[1,2]}$ In particular, finding of compounds that present transition metals with unusual oxidation states or reactive oxygen species (superoxido, peroxido and oxygen...
The evaporation of fluids on the different patterned surfaces is omnipresent in nature. A
comprehensive study of the evaporation process coupling with the wetting effect through modeling
will give us a complete understanding of the underlying mechanisms and help us construct a digital
twin, enabling us to control the whole system. The poster is divided into two parts. Firstly, based on
the...
Using hard coherent x-rays, as produced in PETRA III at DESY, objects of μm length-scale can be imaged with full-field phase-contrast imaging. A recorded single-pulse hologram of the object under investigation in a lens-less imaging setup is disturbed by illumination artifacts. The origin of these artifacts lies in aberrations in the optics, such as figure errors and surface roughness. For...
The unambiguous detection of dark matter requires compatible signals from complementary searches. In this regard, global fits can help us understand if observed excesses and limits agree with each other. To this end, we present the global fitting software GAMBIT (Global and Modular BSM Inference Tool). We exploit GAMBIT’s modularity to implement a new likelihood for the AMS-02 antiproton data,...
We report high-frequency ESR studies on a powder sample of the frustrated quasi-1D spin-1/2 chain material PbCuSeO$_4$(OH)$_2$, isostructural to the well studied natural mineral linarite (PbCuSO$_4$(OH)$_2$). Magnetisation data show the evolution of a magnetically ordered phase below $T_{\rm N}$ = 4.3~K and a spin-flop transition at $B_{\rm SF}$ = 2.8~T.
ESR measurements on a loose powder...
N- and p-channel metal oxide semiconductor field effect transistors (N-MOSFETs, P-MOSFETs) have a wide range of applications today but have their limits to operate in harsh environments with temperatures above 300°C or with high rates of radiation. Transistors realized with Silicon Carbide (SiC) as compound semiconductor are candidates to overcome these issues and have been used as power...
The femtosecond sublattice dynamics in the antiferromagnetically ordered phase of the semiconductor $\alpha$-MnTe are calculated using the linear spin wave theory [1]. We assume that collective lattice vibrations generated by laser pulses induce an oscillating Heisenberg coupling and thus a driving that generates magnons. The calculated antiferromagnetic order parameter shows damped coherent...
Why do we exist? How the observed Baryon Asymmetry in the Universe (BAU) came to be cannot be explained within the Standard Model of Particle Physics (SM). While the Electroweak Phase Transition (EWPhT) has all the ingredients nececessary for baryogenesis, it lacks quantitatively in two points: the phase transition is not strongly first order and the SM does not provide enough CP-violation....
Encapsulation of graphene into in hexagonal Boron Nitride (hBN) has been central to a lot of the research done on graphene in the recent years. Furthermore, graphite top and bottom gates can be added to increase the sample quality. In Bernal stacked bilayer graphene, gate tuning allows to tune control the charge density as well as the out-of-plane electric field independently from one another,...
Photoelectron momentum microscopy is used to study the dispersion of electronic properties at the Fermi level, states of the valence band using photoelectron energy, momentum and spin analysis. We investigated crystalline samples of Mo and Ge on circular dichroism in the angular distribution (CDAD). The results were obtained on the P22 and P04 hard and soft X-ray lines at the PETRA-III...
Recent breakthroughs with ultracold-atom-based programmable quantum simulators have started to show the potential of tweezer arrays as a quantum simulation platform.
A promising application is the simulation of many-body systems like the Ising or Hubbard models.
Our goal is to unite these two capabilities in a novel programmable quantum simulator based on the alkaline-earth atom strontium.
A...
The research project is located in the context of lightweight materials design and is
concerned with the topology optimization of novel foams with regard to best possible foam
structures under mechanical compressive/tensile load. The methods for topology optimisation are
based on the computer-aided design and characterisation of digital foam structures. The focus of the
project is to create a...
Transition Edge Sensors (TES) are superconducting microcalorimeters that can be used for
single-photon detection at extremely low backgrounds. When they are within their supercon-
ducting transition region ($\sim140~$mK for the TES in this work) small temperature fluctuations
- like the energy deposited by single photons - lead to large variations in resistance. These
variations can be...
We have performed a comprehensive study of the temperature-induced phase-transition in transition metal dichalcogenide (TMDC) Mo1-XWXTe2 using ARPES, including linear and circular dichroism in the angular distribution (CDAD/LDAD), X-ray photoelectron diffraction (XPD) and spectroscopy (XPS) of the core-levels, Raman and X-ray diffraction (XRD) measurements at
different temperatures. Based on...
Aktuelle Daten zur Situation von Physikerinnen in Deutschland sowie deren Entwicklung in den letzten Jahren werden präsentiert. Während des Studiums und im Berufsleben treten immer wieder Fragen auf wie: „Werden Frauen immer noch benachteiligt?“ oder „Gibt es mittlerweile genügend weibliche Vorbilder in der Physik – gerade auch in Bezug auf die Vereinbarkeit von Familie und Beruf?“ und „Wie...
Rydberg atoms are considered as one of the most promising candidates for quantum technologies. We have realized Rydberg atom excitation using light guided by an optical nanofiber (ONF). The large evanescent field resulting from the strong confinement of light in the ONF serves as a good platform for atom-light interactions. Our experiment consists of an ONF overlapped with a cloud of...
The existence of dark matter has been known for many decades, but its nature remains one of the biggest mysteries of our Universe, suggesting new physics beyond the Standard Model. We consider a class of models that introduces new, dark particles that are strongly coupled to each other and only coupled to the Standard Model through a new massive exchange particle. The dark particles can...
KATRIN has recently reported an unrivalled sub-eV direct constraint of the neutrino mass from tritium beta-decay spectrum measurements [1]. Along with the neutrino-mass search, KATRIN has published first results of searching for a fourth (sterile) neutrino with a mass in the eV-range using the precision beta-decay spectra[2],[3].
The fourth neutrino mass-eigenstate introduces an additional...
The Arctic is a fascinating part of the Earth, remote and inaccessible but so important for the climate. Its now evident role in climate change, such as the loss of sea ice concentration, makes it an even more attractive place to study. The Arctic climate is a highly coupled state between the open ocean, the ice sheet and the atmosphere where they feed back to each other. While the loss of sea...
Over the past decade, synthetic gene networks have been used extensively to explore principles of biological pattern formation as they play a decisive role during biological growth and development processes. Pattern-forming circuits are also of great interest for the development of future biomaterials that respond to and differentiate autonomously with respect to their environment.
Here, we...
Germanium (Ge) and GeSn materials are very promising candidates for complementary metal-oxide-semiconductor electronics and photonics applications due to their high electron mobility and the possibility to achieve direct bandgap by tuning composition or strain. These are excellent perspectives for devices such as lasers, light-emitting diodes, photodetectors, and modulators. The vibrational...
In a future nuclear fusion reactor, the inner wall components facing the deuterium-tritium-plasma will be subjected to a significant flux of helium (He) as a product of the fusion reaction. Tungsten (W) is considered as the most favorable plasma-facing material because of its good thermal properties, low solubility for hydrogen isotopes, and the high energy threshold for physical sputtering....
Beyond the Standard Model, scalar field dark matter may induce distinct variations in fundamental constants, be it through temporal oscillations or transient changes. With a novel approach, the QSNET project aims to find evidence of new physics by linking observed variations in atomic transition frequencies in a network of ultraprecise atomic, highly charged ion (HCI) as well as molecular...
In the field of optical microscopy, the size range of biological and medical samples of interest varies from single biomolecules (nanometer scale) to whole animal organs (centimeter scale). Since this size range spans across 7 orders of magnitude, different optical tools are needed to analyze such samples across these scales. The mesoscopic size range is concerned with the larger structure of...
Internal interfaces between two solids play a decisive role in modern materials sciences and their technological applications. Among the most prominent examples are certainly semiconductor devices which have been miniaturized to such an extent that their optical and electronic properties are determined decisively by the interfaces.
Two-dimensional heterostructures of transition metal...
The Antimatter Experiment: Gravity, Interferometry, Spectroscopy (AEgIS) collaboration, based at CERN's Antiproton Decelerator (AD) complex, is working towards the production of a pulsed horizontal beam of antihydrogen atoms. The detection of the vertical deflection of such a beam will provide a direct measurement of the gravitational acceleration of antimatter and thus constitute a novel way...
Detailed insight into the dynamics and other functionalities of synthetic polymers on the molecular level is highly desired in advancing nano-technology; however, often, it can be technically challenging. We investigate the dynamics in individualized polymeric chains employing broadband dielectric spectroscopy (BDS). This method revealed altered dynamics under conditions of spatial confinement...
Although crystallization of polymers has been investigated since decades, it is not yet fully understood. One way to gain more insight is to study the difference between bulk polymer and confined polymer chains with focus on how crystallization characteristics change depending on the size and type of confinement. Until now, most studies have used confinement in thin films or nanopores but the...
Since photons are robust carriers of information, photon-based qubits provide a promising platform for efficient error- and resource-reduced all-optical quantum computing [1,2]. When interfacing photons with matter to so-called polaritons, they additionally inherit strong particle-particle interactions [3,4]. By coupling the photons to highly-excited Rydberg states, long storage times can be...
Traveling wave parametric amplifiers (TWPAs) are not only promising candidates to achieve broadband amplification of small quantum signals at quantum limited noise. Beyond that, they have been successfully applied to realize quantum optics experiments in the microwave regime [Esposito et. al., PRL 128(15), 2022] and might even become key tools to generate multi-mode entanglement. However, in...
Helium droplets have a uniquely simple electronic structure, making them ideal targets for light-matter interaction studies. The recent development of intense X-ray pulses from free-electron lasers (FELs) and High-Harmonic Generation (HHG) sources has opened new ways to investigate individual helium nanodroplets with coherent diffraction imaging (CDI) [1,2]. From the diffraction patterns, the...
Single photon sources are highly sought after because photons are excellent quantum information carriers, and are important for quantum communication and fundamental quantum optics. We use a ladder energy level system on the 5S$_{1/2}$-5P$_{3/2}$-5D$_{3/2}$ states of thermal $^{87}$Rb vapour to produce a heralded single photon source with a heralded auto-correlation value of $g^2(\tau = 0) =...
The viscous fingering instability occurs when a more viscous fluid is displaced by a less
viscous one in a Hele-Shaw cell. Instabilities at the interface form a variety of complex patterns via
tip splitting. In this work, we adopt the phase field method coupling with Navier Stokes equations
via surface tension to investigate the influence of several force combinations, such as...
