259 research outputs found
Parution. Thiaroye 44. Scénario inédit
No full textThiaroye 44. Scénario inédit Ben Diogaye Beye et Boubacar Boris Diop Présenté par Martin Mourre et Roger Little Le 1er décembre 1944 au camp militaire de Thiaroye à proximité de Dakar a lieu le massacre de tirailleurs par l'armée française. Si l'expression « Thiaroye 44 » est ancrée dans la mémoire sénégalaise, on sait moins qu'elle provient du projet d'un film au début des années 1980. Le texte présenté ici est le scénario technique de ce projet. Écrit par Ben Diogaye Beye et Boris Boubacar ..
Transient gratings with X-rays
No full textShort period, femtosecond transient gratings in a sample can now be produced by X-rays. The approach promises to reveal the excitation behaviour of complex materials with high temporal and spatial resolution
Untersuchung von VO Mikrostrukturen durch abbildende Spektroskopie mit weicher Röntgenstrahlung
No full textThis bachelor thesis investigates VO microstructures. More specifically, the special property of the phase transition of VO is examined in more detail. Based on the investigationsof Jan O. Schunck et al. who investigated V0 microstructures and found that the phasetransition for their chosen sample structure occurs faster at the edges of the structurethan at the centres of the sample structure, for this experiment the investigated structures were changed, di↵erent film thicknesses of VO were investigated and the temperaturerange considered for the photon yield was extended. Furthermore, a wider temperaturerange was considered and heated up as well as cooled down. The focus was placed oninvestigating how the edges and the centres of the selected structures behave and whatdi↵erences they show in their phase transition. The method of investigation was X-rayabsorption with soft X-rays in combination with imaging through a zone plate, whichallowed us to achieve a resolution of 1 µm. The experiment was carried out at DESY atthe ring accelerator PETRA III at Branch P04. The investigation of VO microstructurescontributes a large part to the development of future technical devices that make use ofthe phase transition of VO and the associated change in its crystal structure, electronicstructure and the change in the optical properties of VO
From Linear to Non-Linear X-ray Spectroscopy on Materials using SASE-FELs
No full textThe key feature of X-ray Free Electron Lasers (XFELs) is their capability to generate ultrashort and at least partially coherent X-ray pulses with extreme intensity. This capability holds the promise to revolutionize X-ray physics in a way similar to how lasers have revolutionized optics, as the non-linear and coherent interactions known from theoptical regime combined with the properties of X-ray radiation could enable techniques with unprecedented analyzing power. This thesis summarizes several contributions tothe development from linear to non-linear X-ray spectroscopies at XFELs. To begin with, I address the technical challenge of normalizing the spectral intensity fluctuationsof XFEL-radiation by presenting several versions of the split-beam normalization scheme. Versions suitable for both monochromatic and broadband measurements, either in transmission through liquids or metal films or in reflection from bulk-supported samples are demonstrated and their capabilities and performance are compared. Moving to non-parametric high-fluence studies, we present a non-linear absorption study at the nickel L3-edge using a monochromatic split-beam normalization scheme. We interpret the fluence-dependent spectral changes by characterizing the evolution of the electronic system during interaction with the X-ray pulse using a rate model that quantifiesthe photon absorption and electronic scattering processes. Further, we show a similar non-linear absorption experiment that utilizes a broadband split-beam normalization scheme. While we observe a comparable evolution ofthe electronic system, the broadband incident radiation leads to a strong contribution of stimulated inelastic scattering that is up to six orders of magnitude stronger than the spontaneous contribution that is exploited in conventional Resonant Inelastic X-rayScattering (RIXS). Finally, we demonstrate sum and difference frequency generation between core-resonant XFEL-photons with two infrared photons for the first time. The observed photon-energy dependence of the third-order non-linear susceptibility suggests an enhancement through coupling between the 1s2p and 1s2s excited states, thus demonstratinga key capability of wave-mixing spectroscopy methods. In summary, the presented work contributes to the development of non-linear X-rayspectroscopy on various fronts, but further developments will be needed to bring X-ray wave-mixing techniques into their preconceived position to deliver unprecedented insights into molecular and solid-state dynamics
Multidimensional and Multimodal Soft X-ray Methods for Quantum Materials Research
No full textQuantum materials are governed by a complex interplay of spin, orbit, charge and lattice degrees of freedom, resulting in emergent phenomena like high-temperature superconductivity, charge and orbital ordering and insulator-to-metal transitions (IMTs). Often, the interaction of these subsystems results in an energy landscape with multiple local minima favouring different phases. In many cases, two or more distinct phases coexist and the macroscopic property of the material is shaped by the properties of the individual phases as well as their interaction. To understand the complexity that shapes quantum materials, their properties need to be studied in multiple dimensions of space, energy and time.X-rays are indispensable tools for the study of quantum materials as they enable probing on atomic length scales as well as excitation of electrons bound in specific core levels. Synchrotron radiation sources provide the coherence, spectral brightness, flexible focusing capabilities and tunability of the photon energy to adapt the X-ray beam properties to the requirements of a specific measurement scheme and sample. The photon energy can be tuned to electronic resonances of one element to disentangle its role for macroscopic functionality. Free-electron lasers (FELs) extend this capability in the time domain down to pico- and femtoseconds, the time scales of atomic and electronic motion.This thesis presents the development of multidimensional and multimodal soft X-ray methods that can be tailored to address specific scientific challenges posed by quantum materials. Multidimensional studies of incident and emitted photon energies and spatial and temporal dependencies as well as the dependence on fluence of a pump laser that drives e.g. an IMT are discussed. Multimodal studies allow observing quantum materials from the point of view of different experimental techniques, like X-ray imaging, X-ray absorption spectroscopy, X-ray emission spectroscopy, (resonant) X-ray diffraction, resonant inelastic X-ray scattering (RIXS) and angle-resolved photoemission spectroscopy (ARPES).First, the RIXS imaging method, which utilizes a transmission Fresnel zone plate to combine soft X-ray absorption spectroscopy with microscopy with a resolution of 1.8 µm, is presented. This method is applied in a study of the IMT of VO microsquares measuring 30 µm 30 µm. Imaging X-ray absorption spectroscopy (XAS) shows that the phase transition temperature at the edges of the squares is lower in comparison to the centres by 1.2 K. This implies that bulk properties of quantum materials may change upon structuring on the microscale.Second, this method is transferred to imaging X-ray diffraction (XRD) to investigate the doped titanate YCaTiO with , revealing insulating and metallic phases which coexist in curved, striped domains across unusually large temperature regions. This observation is related to a varying chemical inhomogeneity of about , likely arising during crystal growth.Next, excitation of the electronic subsystem in quantum materials with femtosecond infra-red laser pulses also drives insulator-to-metal transitions. For the study of ultrafast dynamics of magnetite (FeO) at an FEL, zone plates can also be used for time-to-space mapping, recording a delay range of several picoseconds as well as an extended fluence range simultaneously. This time-to-space mapping setup combines temporal, spatial and pump fluence information and may be developed to record single-shot experiments in the future.Lastly, a method, termed photoelectron spectrometry for the analysis of X-rays (PAX), which converts RIXS photons to photoelectrons via the photoelectric effect, is developed towards high energy resolution to investigate a sample from the family of high-temperature superconducting cuprates. PAX enables simultaneous recording of a range of photon-sample momentum transfer, corresponding to a significant part of the first Brillouin zone in the investigated system. In comparison to grating-based RIXS spectrometers, a PAX instrument is much more compact, saving money and experimental space. The success of the PAX method resulted in the development of a dedicated ultra-high vacuum chamber, soon to be commissioned, which promises a significant improvement in photon count rate and energy resolution, as well as the combination with ARPES.In summary, this thesis presents experimental developments that enable the study of quantum materials through the utilisation of diverse soft X-ray methods in conjunction with a spatial resolution on the micrometer level, temporal resolution on the level of 100 fs and energy resolution on the level of 100 meV. Furthermore, it outlines concepts to improve this energy and spatial resolution by approximately one order of magnitude. The advancement of the experimental tools described in this thesis will facilitate a deeper comprehension of the complexity of quantum materials and enable us as a society to harness phenomena occurring in quantum materials
Full-field Bragg imaging of microscopic domains in a quantum material with phase coexistence
No full textYCaTiO is a quantum material that experiences a highly unusual metal-insulator transition: Across a very large temperature range between 100 K and 200 K, this material turns from conductive at low temperatures to being insulating at higher temperatures, which is the opposite transition of materials with similar properties such as VO. Earlier studies demonstrated that within this temperature range, the material exists in two different phases that grow in elongated domains: A conductive orthorhomic phase and an insulating monoclinic phase. The latter phase is less symmetric and has a Bragg reflection at the (011) plane which is missing for the conductive phase. By taking advantage of the different reflection conditions, the emergence and growth of the insulating phase domains and thereby the metal-insulator-transition can directly be imaged. The present experiment uses soft x-rays from the highly brilliant synchrotron radiation source PETRA III and an off-axis Fresnel zone plate to achieve a Bragg imaging resolution of about 1μm over a simultaneous field of view of 1 x 1 mm. The implementation of this setup reveals that YCaTiO has microscopic stripes whose crystalline structure differs greatly from the adjacent stripe edges during temperature changes. The monoclinic insulating phase appears at strikingly different temperatures for different regions of the sample
Combining resonant inelastic X-ray scattering with micrometer resolution to image electronic properties of quantum materials
No full textThis thesis presents developments and results of an experimental setup which combines soft X-ray spectroscopy methods for electronic structure analysis and imaging capabilities with the goal to gain detailed understanding of quantum materials, which exhibit spatial electronic inhomogeneities. The setup features a combination of two Fresnel zone plates which are about 1mm long and sub-μm wide: Firstly, a linear illumination zone plate creates a vertical X-ray focus line on the sample. Secondly, an off-axis zone plate, located between the sample and the two-dimensional detector, disperses X-rays emitted from the sample in horizontal direction, while also imaging the sample onto the detector at the same time. In this way, a 2D map is created on the detector which, in the vertical dimension, contains information on the position on the sample from where the X-rays are emitted, and in the horizontal dimension resolves the photon energies emitted from the sample. The presented experiment was performed at the soft X-ray beamline P04 of the synchrotron radiation source PETRA III at the DESY research facility in Hamburg. In the first part of the experiment, the spatial resolution of the setup was determined to be better than 3 μm. Secondly, this spatial resolution was combined with X-ray absorption (XAS) and resonant inelastic X-ray scattering (RIXS) measurements at the oxygen Kedge to investigate the insulator-to-metal phase transition of VO2 microsquares with an edge length of 30 μm. These structures were studied, in order to answer the question if the phase transition behaviour is different in structured parts of a sample, where the defect density at the edges of structures may act as nucleation centres. This is compared to the central area of the squares acting as a model for a bulk material reference. This is an important step towards functionalising phase transitions in complex materials, where insights from bulk materials may not readily be transferred to structured devices
Von linearer zu nichtlinearer Röntgenspektroskopie an Materialien mittels SASE-FELs
No full textThe key feature of X-ray Free-Electron Lasers (XFELs) is their capability to generate ultrashort and at least partially coherent X-ray pulses with extreme intensity. This capability holds the promise to revolutionize X-ray physics in a way similar to how lasers have revolutionized optics, as the non-linear and coherent interactions known from the optical regime combined with the properties of X-ray radiation could enable techniques with unprecedented analyzing power.
This thesis summarizes several contributions to the development from linear to non-linear X-ray spectroscopies at XFELs.
To begin with, I address the technical challenge of normalizing the spectral intensity fluctuations of XFEL-radiation by presenting several versions of the split-beam normalization scheme. Versions suitable for both monochromatic and broadband measurements, either in transmission through liquids or metal films or in reflection from bulk-supported samples are demonstrated and their capabilities and performance are compared.
Moving to non-parametric high-fluence studies, we present a non-linear absorption study at the nickel L3-edge using a monochromatic split-beam normalization scheme.
We interpret the fluence-dependent spectral changes by characterizing the evolution of the electronic system during interaction with the X-ray pulse using a rate model that quantifies the photon absorption and electronic
scattering processes.
Further, we show a similar non-linear absorption experiment that utilizes a broadband split-beam normalization scheme. While we observe a comparable evolution of the electronic system, the broadband incident radiation leads to a strong contribution of stimulated inelastic scattering that is up to six orders of magnitude stronger than the spontaneous contribution that is exploited in conventional Resonant Inelastic X-ray Spectroscopy (RIXS).
Finally, we demonstrate sum and difference frequency generation between core-resonant XFEL-photons with two infrared photons for the first time. The observed photon-energy dependence of the third-order non-linear susceptibility suggests an enhancement through coupling between the 1s2p and 1s2s excited states, thus demonstrating a key capability of wave-mixing spectroscopy methods.
In summary, the presented work contributes to the development of non-linear X-ray spectroscopy on various fronts, but further developments will be needed to bring X-ray wave-mixing techniques into their preconceived position to deliver unprecedented insights into molecular and solid-state dynamics.Die wichtigste Eigenschaft von Röntgen-Freie-Elektronen-Lasern (XFELs) ist ihre Fähigkeit, ultrakurze und zumindest teilweise kohärente Röntgenpulse mit extrem hoher Intensität zu erzeugen.
Daraus ergibt sich die Hoffnung, die Methoden der Röntgenphysik in ähnlicher Weise zu revolutionieren wie man es mit optischen Messmethoden durch die Einführung des Lasers vermochte, da die aus dem optischen Bereich bekannten nichtlinearen und kohärenten Wechselwirkungen kombiniert mit den Eigenschaften von Röngenstrahlung nie dagewesene Messungen ermöglichen könnten.
In dieser Doktorarbeit werden mehrere Beiträge zur Entwicklung von linearer zu nicht-linearer Röntgenspektroskopie an XFELs zusammengefasst.
Zunächst behandle ich die technische Herausforderung, die inhärenten spektralen Intensitätsfluktuationen von XFEL-Strahlung zu normalisieren, indem ich verschiedene Realisierungen des Split-Beam Normalisierungsprinzips vorstelle.
Die verschiedenen Aufbauten benutzen jeweils monochromatische und breitbandige Strahlung und sind jeweils für Transmissionmessungen durch dünne Filme und für Reflexionsmessungen von massiven Proben konzipiert. Ihre jeweiligen Vor- und Nachteile sowie die erreichte Sensitivität werden verglichen.
Daraufhin stelle ich eine nicht-parametrisch nichtlineare Absorptionsstudie an der Nickel L3 Absorptionskante vor, für welche ebenfalls monochromatische Split-Beam-Normalisierung genutzt wurde.
Wir interpretieren die fluenzabhängigen spektralen Veränderungen anhand der Evolution des elektronischen Systems während der Interaktion mit dem Röntgenpuls durch ein Ratenmodell, das die Absorption von Photonen und die Raten der elektronischen Streuprozesse quantifiziert.
Des Weiteren zeigen wir ein ähnliches nichtlineares Absorptionsexperiment mit einem breitbandigem Split-Beam Normalisierungsschema.
Während eine vergleichbare Evolution des elektronischen Systems beobachtet wird, ermöglicht die breitbandig einfallende Strahlung einen wesentlichen Beitrag von stimulierter inelastischer Streuung, der bis zu sechs Größenordnungen stärker ist als der spontane Beitrag, welcher in konventionellen Messungen von Resonanter Inelastischer X-ray Streuung (RIXS) genutzt wird.
Schließlich demonstrieren wir zum ersten Mal Summen- und Differenzfrequenzgenerierung zwischen XFEL-Photonen und zwei Infrarotphotonen.
Die beobachtete Photonenenergie-Abhängigkeit der nichtlinearen Suszeptibilität deutet auf eine Verstärkung des Signals durch die Kopplung zwischen den exzitonischen Konfigurationen 1s2p und 1s2s hin, was ein wesentliches Alleinstellungsmerkmal von Wellenmischungs-Experimenten demonstriert.
Zusammenfassend tragen die vorgestellten Arbeiten auf mehreren Wegen zur Forschung an nichtlinearer Röntgenspektroskopie bei. Allerdings werden weitere Entwicklungen benötigt um das Potential von Röntgenbasierten Wellenmischungs-Techniken für regelmäßige neue Einblicke in die Dynamik von Molekülen und Festkörpern zu umzusetzen
Multidimensional and Multimodal Soft X-ray Methods for Quantum Materials Research
No full textQuantum materials are governed by a complex interplay of spin, orbit, charge and lattice degrees of freedom, resulting in emergent phenomena like high-temperature superconductivity, charge and orbital ordering and insulator-to-metal transitions (IMTs). Often, the interaction of these subsystems results in an energy landscape with multiple local minima favouring different phases. In many cases, two or more distinct phases coexist and the macroscopic property of the material is shaped by the properties of the individual phases as well as their interaction. To understand the complexity that shapes quantum materials, their properties need to be studied in multiple dimensions of space, energy and time.
X-rays are indispensable tools for the study of quantum materials as they enable probing on atomic length scales as well as excitation of electrons bound in specific core levels. Synchrotron radiation sources provide the coherence, spectral brightness, flexible focusing capabilities and tunability of the photon energy to adapt the X-ray beam properties to the requirements of a specific measurement scheme and sample. The photon energy can be tuned to electronic resonances of one element to disentangle its role for macroscopic functionality. Free-electron lasers (FELs) extend this capability in the time domain down to pico- and femtoseconds, the time scales of atomic and electronic motion.
This thesis presents the development of multidimensional and multimodal soft X-ray methods that can be tailored to address specific scientific challenges posed by quantum materials. Multidimensional studies of incident and emitted photon energies and spatial and temporal dependencies as well as the dependence on fluence of a pump laser that drives e.g. an IMT are discussed. Multimodal studies allow observing quantum materials from the point of view of different experimental techniques, like X-ray imaging, X-ray absorption spectroscopy, X-ray emission spectroscopy, (resonant) X-ray diffraction, resonant inelastic X-ray scattering (RIXS) and angle-resolved photoemission spectroscopy (ARPES).
First, the RIXS imaging method, which utilizes a transmission Fresnel zone plate to combine soft X-ray absorption spectroscopy with microscopy with a resolution of 1.8 µm, is presented. This method is applied in a study of the IMT of VO2 microsquares measuring 30 µm × 30 µm. Imaging X-ray absorption spectroscopy (XAS) shows that the phase transition temperature at the edges of the squares is lower in comparison to the centres by 1.2 K. This implies that bulk properties of quantum materials may change upon structuring on the microscale.
Second, this method is transferred to imaging X-ray diffraction (XRD) to investigate the doped titanate Y1−xCaxTiO3 with x = 0.37, revealing insulating and metallic phases which coexist in curved, striped domains across unusually large temperature regions. This observation is related to a varying chemical inhomogeneity of about x ± 0.01, likely arising during crystal growth.
Next, excitation of the electronic subsystem in quantum materials with femtosecond infra-red laser pulses also drives insulator-to-metal transitions. For the study of ultrafast dynamics of magnetite (Fe3O4) at an FEL, zone plates can also be used for time-to-space mapping, recording a delay range of several picoseconds as well as an extended fluence range simultaneously. This time-to-space mapping setup combines temporal, spatial and pump fluence information and may be developed to record single-shot experiments in the future.
Lastly, a method, termed photoelectron spectrometry for the analysis of X-rays (PAX), which converts RIXS photons to photoelectrons via the photoelectric effect, is developed towards high energy resolution to investigate a sample from the family of high-temperature superconducting cuprates. PAX enables simultaneous recording of a range of photon-sample momentum transfer, corresponding to a significant part of the first Brillouin zone in the investigated system. In comparison to grating-based RIXS spectrometers, a PAX instrument is much more compact, saving money and experimental space. The success of the PAX method resulted in the development of a dedicated ultra-high vacuum chamber, soon to be commissioned, which promises a significant improvement in photon count rate and energy resolution, as well as the combination with ARPES.
In summary, this thesis presents experimental developments that enable the study of quantum materials through the utilisation of diverse soft X-ray methods in conjunction with a spatial resolution on the micrometer level, temporal resolution on the level of 100 fs and energy resolution on the level of 100 meV. Furthermore, it outlines concepts to improve this energy and spatial resolution by approximately one order of magnitude. The advancement of the experimental tools described in this thesis will facilitate a deeper comprehension of the complexity of quantum materials and enable us as a society to harness phenomena occurring in quantum materials.Quantenmaterialien werden durch ein komplexes Zusammenspiel von Spin, Orbit, Ladung und Kristallgitter charakterisiert, was emergente Phänomene wie Hochtemperatursupraleitung, Ladungs- und Orbitalordnung und Isolator-Metall-Übergänge hervorrufen kann. Häufig erzeugt die Wechselwirkung dieser Freiheitsgrade eine Energielandschaft mit mehreren lokalen Minima, welche verschiedene Phasen begünstigen. Dies kann dazu führen, dass zwei oder mehr unterschiedliche Phasen koexistieren und die makroskopische Eigenschaft des Materials durch die Eigenschaften der einzelnen Phasen sowie deren Wechselwirkung bestimmt wird. Um diese Komplexität, welche Quantenmaterialien charakterisiert, zu verstehen, müssen ihre Eigenschaften in den Dimensionen von Raum, Energie und Zeit untersucht werden.
Röntgenstrahlen sind unverzichtbare Werkzeuge für die Untersuchung von Quantenmaterialien, da sie die Untersuchung auf atomaren Längenskalen sowie die Anregung von Elektronen, gebunden in spezifischen Kernniveaus, ermöglichen. Synchrotronstrahlungsquellen bieten die Kohärenz, spektrale Helligkeit, flexible Fokussierungsmöglichkeiten und Durchstimmbarkeit der Photonenenergie, welche nötig sind um die Eigenschaften des Röntgenstrahls an die Anforderungen eines bestimmten Messschemas und einer bestimmten Probe anzupassen. Die Photonenenergie kann auf elektronische Resonanzen eines Elements eingestellt werden, um dessen Beitrag zu der makroskopischen Funktionalität zu untersuchen. Freie-Elektronen-Laser (FELs) erweitern diese Möglichkeiten hin zu den Zeitskalen von Piko- und Femtosekunden, auf welchen sich Atome und Elektronen bewegen.
Diese Dissertation beschreibt die Entwicklung von multidimensionalen und multimodalen Weichröntgenmethoden, welche auf die spezifischen wissenschaftlichen Herausforderungen von Quantenmaterialien angepasst werden. Multidimensionale Studien von einfallender und emittierter Photonenenergie, von räumlichen und zeitlichen
Abhängigkeiten sowie von der Abhängigkeit der Fluenz eines Pumplasers, welcher einen Isolator-Metallübergang anregt, werden diskutiert. Multimodale Studien ermöglichen die Beobachtung von Quantenmaterialien mit verschiedenen experimentellen Techniken, wie Röntgenbildgebung, Röntgenabsorptionsspektroskopie, Röntgenemissionsspektroskopie, (resonanter) Röntgendiffraktion, resonanter inelastischer Röntgenstreuung (RIXS) und winkelaufgelöster Photoemissionsspektroskopie (ARPES).
Zunächst wird eine abbildende RIXS Methode vorgestellt, welche eine Transmissions-Fresnel-Zonenplatte verwendet um Weichröntgenabsorptionsspektroskopie mit Mikroskopie mit einer Auflösung von 1.8 μm zu kombinieren. Diese Methode wird in einer Studie des Isolator-Metallübergangs von Mikroquadraten, welche 30 μm×30 μm klein sind und aus Vanadiumdioxid (VO2) bestehen, angewendet. Abbildende Röntgenabsorptionsspektroskopie (XAS) zeigt, dass die Phasenübergangstemperatur an den Rändern der Quadrate im Vergleich zu den Zentren um 1.2K verringert ist. Dies deutet darauf hin, dass sich die Eigenschaften von Quantenmaterialien durch Strukturierung auf der Mikroskala ändern können.
Weiterhin wird diese Methode auf abbildende Röntgenbeugung (XRD) übertragen, um das dotierte Titanatsystem Y1 − xCaxTiO3 mit x = 0.37 zu untersuchen. Hierbei werden isolierende und metallische Phasen beobachtet, welche in gekrümmten, streifenförmigen Domänen über ungewöhnlich große Temperaturbereiche hinweg koexistieren. Diese Beobachtung steht in Zusammenhang mit einer variierenden chemischen Inhomogenität von etwa x±0.01, die wahrscheinlich während des Kristallwachstums entstanden ist.
Auch Femtosekunden-Infrarot-Laserpulse können genutzt werden, um das elektronische System in Quantenmaterialien anzuregen und Isolator-Metall-Übergänge zu treiben. Für die Untersuchung der ultraschnellen Dynamik von Magnetit (Fe3O4) an einem FEL können Zonenplatten auch für die Methode des Time-to-Space Mapping verwendet werden, wobei eine Spanne des Zeitversatzes zwischen Pumplaser und FEL von mehreren Pikosekunden sowie eine Verteilung von Fluenzen gleichzeitig aufgezeichnet werden. Diese Methode kombiniert Informationen über Zeit, Raum und Pumpfluenz und kann in Zukunft für die Aufzeichnung von Einzelschussexperimenten entwickelt werden.
Schließlich wird die Methode der Photoelektronenspektrometrie zur Analyse von Röntgenstrahlung (PAX) weiterentwickelt. Diese Methode wandelt RIXS-Photonen mit Hilfe des photoelektrischen Effekts in Photoelektronen um. Sie wird genutzt um eine Probe aus der Familie der Hochtemperatursupraleiter mit hoher Energieauflösung zu untersuchen. Weiterhin ermöglicht PAX die simultane Messung einer Verteilung von Impulsüberträgen von Photonen auf die Probe. Der Bereich der Verteilung
entspricht einem signifikanten Teil der ersten Brillouin-Zone in dem hier untersuchten System. Im Vergleich zu Gitterspektrometern ist ein PAX-Instrument viel kompakter, was Geld und Experimentierfläche spart. Der Erfolg der PAX-Methode führte zur Entwicklung einer speziellen Ultrahochvakuumkammer, die demnächst in Betrieb genommen wird und eine erhebliche Verbesserung der Photonenzählrate und der Energieauflösung sowie die Kombination mit ARPES verspricht.
Zusammenfassend werden in dieser Arbeit experimentelle Entwicklungen vorgestellt, welche die Untersuchung von Quantenmaterialien durch den Einsatz verschiedener Weichröntgenmethoden in Verbindung mit einer räumlichen Auflösung im Mikrometerbereich, einer Zeitauflösung im Bereich von 100 fs und einer Energieauflösung im Bereich von 100 meV ermöglichen. Darüber hinaus werden Konzepte zur Verbesserung dieser Energie- und Ortsauflösung um etwa eine Größenordnung vorgestellt. Die Weiterentwicklung der in dieser Arbeit beschriebenen experimentellen Werkzeuge wird ein tieferes Verständnis der Komplexität von Quantenmaterialien ermöglichen und uns als Gesellschaft in die Lage versetzen, Phänomene, die in Quantenmaterialien auftreten, nutzbar zu machen
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