@article{OPUS4-31268,
  title     = {Search for new phenomena in events with same-charge leptons and b-jets in pp collisions at √\(s\) = 13 TeV with the ATLAS detector},
  series = {Journal of High Energy Physics},
  volume    = {12},
  journal   = {Journal of High Energy Physics},
  number    = {39},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1007/JHEP12(2018)039},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312681},
  pages     = {1-55},
  year      = {2018},
  abstract  = {A search for new phenomena in events with two same- charge leptons or three leptons and jets identi fi ed as originating from b - quarks in a data sample of 36.1 fb of pp collisions at ps = 13TeV recorded by the ATLAS detector at the Large Hadron Collider is reported. No signi fi cant excess is found and limits are set on vector- like quark, fourtop- quark, and same- sign top- quark pair production. The observed ( expected) 95\% CL mass limits for a vector- like T - and B - quark singlet are mT > 0 : 98 ( 0 : 99) TeV and mB > 1 : 00 ( 1 : 01) TeV respectively. Limits on the production of the vector- like T5=3 - quark are also derived considering both pair and single production; in the former case the lower limit on the mass of the T5=3 - quark is ( expected to be) 1.19 ( 1.21) TeV. The Standard Model fourtop- quark production cross- section upper limit is ( expected to be) 69 ( 29) fb. Constraints are also set on exotic four- top- quark production models. Finally, limits are set on samesign top- quark pair production. The upper limit on uu ! tt production is ( expected to be) 89 ( 59) fb for a mediator mass of 1TeV, and a dark- matter interpretation is also derived, excluding a mediator of 3TeV with a dark- sector coupling of 1.0 and a coupling to ordinary matter above 0.31.},
  language  = {en}
}
@phdthesis{Kagerer2024,
  author    = {Kagerer, Philipp Thomas},
  title     = {Two-Dimensional Ferromagnetism and Topology at the Surface of MnBi\(_2\)Te\(_4\) - Bi\(_2\)Te\(_3\) Heterostructures - MBE Growth, Magnetism and Electronic Properties},
  doi       = {10.25972/OPUS-36012},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-360121},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {In this thesis, a model system of a magnetic topological heterostructure is studied, namely a heterosystem consisting of a single ferromagnetic septuple-layer (SL) of \(MnBi_2Te_4\) on the surface of the three-dimensional topological insulator \(Bi_2Te_3\). Using MBE and developing a specialized experimental setup, the first part of this thesis deals with the growth of \(Bi_2Te_3\) and thin films of \(MnBi_2Te_4\) on \(BaF_2\)-substrates by the co-evaporation of its binary constituents. The structural analysis is conducted along several suitable probes such as X-ray diffraction (XRD, XRR), AFM and scanning tunnelling electron microscopy (STEM). It is furthermore found that the growth of a single septuple-layer of \(MnBi_2Te_4\) on the surface of \(Bi_2Te_3\) can be facilitated. By using X-ray absorption and circular magnetic dichroism (XAS, XMCD), the magnetic properties of \(MnBi_2Te_4\) are explored down to the monolayer limit. The layered nature of the vdW crystal and a strong uniaxial magnetocrystalline anisotropy establish stable out-of plane magnetic order at the surface of \(MnBi_2Te_4\), which is stable even down to the 2D limit. Pushing the material system to there, i.e. a single SL \(MnBi_2Te_4\) further allows to study the phase transition of this 2D ferromagnet and extract its critical behaviour with \(T_c \, = \, 14.89~k\) and \(\beta \, = \, 0.484\). Utilizing bulk crystals of the ferromagnetic \(Fe_3GeTe_2\) as substrate allows to influence, enhance and bias the magnetism in the single SL of \(MnBi_2Te_4\). By growing heterostructures of the type \(MnBi_2Te_4\) -- n layer \(Bi_2Te_3\) -- \(Fe_3GeTe_2\)for n between 0 and 2, it is shown, that a considerable magnetic coupling can be introduced between the \(MnBi_2Te_4\) top-layer and the substrate. Finally the interplay between topology and magnetism in the ferromagnetic extension is studied directly by angle-resolved photoemission spectroscopy. The heterostructure is found to host a linearly dispersing TSS at the centre of the Brillouin zone. Using low temperature and high-resolution ARPES a large magnetic gap opening of \(\sim\) 35 meV is found at the Dirac point of the TSS. By following its temperature evolution, it is apparent that the scaling behaviour coincides with the magnetic order parameter of the modified surface.},
  subject      = {Molekularstrahlepitaxie},
  language  = {en}
}
@article{HeDiSanteLietal.2018,
  author    = {He, Jiangang and Di Sante, Domenico and Li, Ronghan and Chen, Xing-Qiu and Rondinelli, James M. and Franchini, Cesare},
  title     = {Tunable metal-insulator transition, Rashba effect and Weyl Fermions in a relativistic charge-ordered ferroelectric oxide},
  series = {Nature Communications},
  volume    = {9},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-017-02814-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-227946},
  year      = {2018},
  abstract  = {Controllable metal-insulator transitions (MIT), Rashba-Dresselhaus (RD) spin splitting, and Weyl semimetals are promising schemes for realizing processing devices. Complex oxides are a desirable materials platform for such devices, as they host delicate and tunable charge, spin, orbital, and lattice degrees of freedoms. Here, using first-principles calculations and symmetry analysis, we identify an electric-field tunable MIT, RD effect, and Weyl semimetal in a known, charge-ordered, and polar relativistic oxide Ag2BiO3 at room temperature. Remarkably, a centrosymmetric BiO6 octahedral-breathing distortion induces a sizable spontaneous ferroelectric polarization through Bi3+/Bi5+ charge disproportionation, which stabilizes simultaneously the insulating phase. The continuous attenuation of the Bi3+/Bi5+ disproportionation obtained by applying an external electric field reduces the band gap and RD spin splitting and drives the phase transition from a ferroelectric RD insulator to a paraelectric Dirac semimetal, through a topological Weyl semimetal intermediate state. These findings suggest that Ag2BiO3 is a promising material for spin-orbitonic applications.},
  language  = {en}
}
@phdthesis{Zhao2024,
  author    = {Zhao, Suting},
  title     = {Symmetry Resolution of Entanglement in Holography},
  doi       = {10.25972/OPUS-36385},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-363854},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {This thesis investigates the charged moments and the symmetry-resolved entanglement entropy in the context of the AdS3/CFT2 duality. In the first part, I focus on the holographic U(1) Chern-Simons-Einstein gravity, a toy model of AdS3/CFT2 with U(1) Kac-Moody symmetry. I start with the vacuum background with a single entangling interval. I show that, apart from a partition function in the grand canonical ensemble, the charged moments can also be interpreted as the two-point function of vertex operators on the replica surface. For the holographic description, I propose a duality between the bulk U(1) Wilson line and the boundary vertex operators. I verify this duality by deriving the effective action for the Chern-Simons fields and comparing the result with the vertex correlator. In the twist field approach, I show that the charged moments are given by the correlation function of the charged twist operators and the additional background operators. To solve the correlation functions involved, I prove the factorization of the U(1) extended conformal block into a U(1) block and a Virasoro block. The general expression for the U(1) block is derived by directly summing over the current descendant states, and the result shows that it takes an identical form as the vertex correlators. This leads to the conclusion that the disjoint Wilson lines compute the neutral U(1) block. The final result for the symmetry-resolved entanglement entropy shows that it is always charge-independent in this model. In the second part, I study charged moments in higher spin holography, where the boundary theory is a CFT with W3 symmetry. I define the notion of the higher spin charged moments by introducing a spin-3 modular charge operator. Restricting to the vacuum background with a single entangling interval, I employ the grand canonical ensemble interpretation and calculate the charged moments via the known higher spin black hole solution. On the CFT side, I perform a perturbative expansion for the higher spin charged moments in terms of the connected correlation functions of the spin-3 modular charge operators. Using the recursion relation for the correlation functions of the W3 currents, I evaluate the charged moments up to the quartic order of the chemical potential. The final expression matches with the holographic result. My results both for U(1) Chern-Simons Einstein gravity and W3 higher spin gravity constitute novel checks of the AdS3/CFT2 correspondence.},
  subject      = {AdS-CFT-Korrespondenz},
  language  = {en}
}
@phdthesis{Wagner2024,
  author    = {Wagner, Tim Matthias},
  title     = {Characterization of 2D antimony lattices},
  doi       = {10.25972/OPUS-36329},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-363292},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {Two-dimensional lattices are in the focus of research in modern solid state physics due to their novel and exotic electronic properties with tremendous potential for seminal future applications. Of particular interest within this research field are quantum spin Hall insulators which are characterized by an insulating bulk with symmetry-protected metallic edge states. For electrons within these one-dimensional conducting channels, spin-momentum locking enables dissipationless transport - a property which promises nothing short of a revolution for electronic devices. So far, however, quantum spin Hall materials require enormous efforts to be realized such as cryogenic temperatures or ultra-high vacuum. A potential candidate to overcome these shortcomings are two-dimensional lattices of the topological semi-metal antimony due to their potential to host the quantum spin Hall effect while offering improved resilience against oxidation. In this work, two-dimensional lattices of antimony on different substrates, namely Ag(111), InSb(111) and SiC(0001), are investigated regarding their atomic structure and electronic properties with complimentary surface sensitive techniques. In addition, a systematic oxidation study compares the stability of Sb-SiC(0001) with that of the two-dimensional topological insulators bismuthene-SiC(0001) and indenene-SiC(0001). A comprehensive experimental analysis of the \((\sqrt{3}\times\sqrt{3})R30^\circ\) Sb-Ag(111) surface, including X-ray standing wave measurements, disproves the proclaimed formation of a buckled antimonene lattice in literature. The surface lattice can instead be identified as a metallic Ag\(_2\)Sb surface alloy. Antimony on InSb(111) shows an unstrained Volmer-Weber island growth due to its large lattice mismatch to the substrate. The concomitant moir\'{e} situation at the interface imprints mainly in a periodic height corrugation of the antimony islands which as observed with scanning tunneling microscopy. On islands with various thicknesses, quasiparticle interference patterns allow to trace the topological surface state of antimony down to the few-layer limit. On SiC(0001), two different two-dimensional antimony surface reconstructions are identified. Firstly, a metallic triangular \$1\times1\$ lattice which constitutes the antimony analogue to the topological insulator indenene. Secondly, an insulating asymmetric kagome lattice which represents the very first realized atomic surface kagome lattice. A comparative, systematic oxidation study of elemental (sub-)monolayer materials on SiC(0001) reveals a high sensitivity of indenene and bismuthene to small dosages of oxygen. An improved resilience is found for Sb-SiC(0001) which, however, oxidizes nevertheless if exposed to oxygen. These surface lattices are therefore not suitable for future applications without additional protective measures.},
  subject      = {Antimon},
  language  = {en}
}
@article{OPUS4-31266,
  title     = {Combination of inclusive and differential t(t)over-bar charge asymmetry measurements using ATLAS and CMS data at root S=7 and 8 TeV},
  series = {Journal of High Energy Physics},
  volume    = {33},
  journal   = {Journal of High Energy Physics},
  number    = {4},
  organization    = {The ATLAS collaboration and the CMS collaboration},
  doi       = {10.1007/JHEP04(2018)033},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312669},
  pages     = {1-67},
  year      = {2018},
  abstract  = {This paper presents combinations of inclusive and differential measurements of the charge asymmetry (A(C)) in top quark pair (t(t)over-bar) events with a lepton+jets signature by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. The data correspond to integrated luminosities of about 5 and 20 fb(-1) for each experiment, respectively. The resulting combined LHC measurements of the inclusive charge asymmetry are A(C)(LHC7) = 0.005 +/- 0.007 (stat) +/- 0.006 (syst) at 7 TeV and A(C)(LHC8) = 0.0055 +/- 0.0023 (stat) +/- 0.0025 (syst) at 8 TeV. These values, as well as the combination of A(C) measurements as a function of the invariant mass of the t(t)over-bar system at 8 TeV, are consistent with the respective standard model predictions.},
  language  = {en}
}
@article{KreinbergPorteSchickeetal.2019,
  author    = {Kreinberg, S{\"o}ren and Porte, Xavier and Schicke, David and Lingnau, Benjamin and Schneider, Christian and H{\"o}fling, Sven and Kanter, Ido and L{\"u}dge, Kathy and Reitzenstein, Stephan},
  title     = {Mutual coupling and synchronization of optically coupled quantum-dot micropillar lasers at ultra-low light levels},
  series = {Nature Communications},
  volume    = {10},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-019-09559-2},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229811},
  year      = {2019},
  abstract  = {Synchronization of coupled oscillators at the transition between classical physics and quantum physics has become an emerging research topic at the crossroads of nonlinear dynamics and nanophotonics. We study this unexplored field by using quantum dot microlasers as optical oscillators. Operating in the regime of cavity quantum electrodynamics (cQED) with an intracavity photon number on the order of 10 and output powers in the 100 nW range, these devices have high β-factors associated with enhanced spontaneous emission noise. We identify synchronization of mutually coupled microlasers via frequency locking associated with a sub-gigahertz locking range. A theoretical analysis of the coupling behavior reveals striking differences from optical synchronization in the classical domain with negligible spontaneous emission noise. Beyond that, additional self-feedback leads to zero-lag synchronization of coupled microlasers at ultra-low light levels. Our work has high potential to pave the way for future experiments in the quantum regime of synchronization.},
  language  = {en}
}
@article{KremerBiesenthalMaczewskyetal.2019,
  author    = {Kremer, Mark and Biesenthal, Tobias and Maczewsky, Lukas J. and Heinrich, Matthias and Thomale, Ronny and Szameit, Alexander},
  title     = {Demonstration of a two-dimensional PT-symmetric crystal},
  series = {Nature Communications},
  volume    = {10},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-018-08104-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230132},
  year      = {2019},
  abstract  = {With the discovery of PT-symmetric quantum mechanics, it was shown that even non-Hermitian systems may exhibit entirely real eigenvalue spectra. This finding did not only change the perception of quantum mechanics itself, it also significantly influenced the field of photonics. By appropriately designing one-dimensional distributions of gain and loss, it was possible to experimentally verify some of the hallmark features of PT-symmetry using electromagnetic waves. Nevertheless, an experimental platform to study the impact of PT-symmetry in two spatial dimensions has so far remained elusive. We break new grounds by devising a two-dimensional PT-symmetric system based on photonic waveguide lattices with judiciously designed refractive index landscape and alternating loss. With this system at hand, we demonstrate a non-Hermitian two-dimensional topological phase transition that is closely linked to the emergence of topological mid-gap edge states.},
  language  = {en}
}
@article{SchneiderGlazovKornetal.2018,
  author    = {Schneider, Christian and Glazov, Mikhail M. and Korn, Tobias and H{\"o}fling, Sven and Urbaszek, Bernhard},
  title     = {Two-dimensional semiconductors in the regime of strong light-matter coupling},
  series = {Nature Communications},
  volume    = {9},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-018-04866-6},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-231295},
  year      = {2018},
  abstract  = {The optical properties of transition metal dichalcogenide monolayers are widely dominated by excitons, Coulomb-bound electron-hole pairs. These quasi-particles exhibit giant oscillator strength and give rise to narrow-band, well-pronounced optical transitions, which can be brought into resonance with electromagnetic fields in microcavities and plasmonic nanostructures. Due to the atomic thinness and robustness of the monolayers, their integration in van der Waals heterostructures provides unique opportunities for engineering strong light-matter coupling. We review first results in this emerging field and outline future opportunities and challenges.},
  language  = {en}
}
@article{SchmittMorasBihlmayeretal.2019,
  author    = {Schmitt, Martin and Moras, Paolo and Bihlmayer, Gustav and Cotsakis, Ryan and Vogt, Matthias and Kemmer, Jeannette and Belabbes, Abderrezak and Sheverdyaeva, Polina M. and Kundu, Asish K. and Carbone, Carlo and Bl{\"u}gel, Stefan and Bode, Matthias},
  title     = {Indirect chiral magnetic exchange through Dzyaloshinskii-Moriya-enhanced RKKY interactions in manganese oxide chains on Ir(100)},
  series = {Nature Communications},
  volume    = {10},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-019-10515-3},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230986},
  year      = {2019},
  abstract  = {Localized electron spins can couple magnetically via the Ruderman-Kittel-Kasuya-Yosida interaction even if their wave functions lack direct overlap. Theory predicts that spin-orbit scattering leads to a Dzyaloshinskii-Moriya type enhancement of this indirect exchange interaction, giving rise to chiral exchange terms. Here we present a combined spin-polarized scanning tunneling microscopy, angle-resolved photoemission, and density functional theory study of MnO2 chains on Ir(100). Whereas we find antiferromagnetic Mn-Mn coupling along the chain, the inter-chain coupling across the non-magnetic Ir substrate turns out to be chiral with a 120° rotation between adjacent MnO2 chains. Calculations reveal that the Dzyaloshinskii-Moriya interaction results in spin spirals with a periodicity in agreement with experiment. Our findings confirm the existence of indirect chiral magnetic exchange, potentially giving rise to exotic phenomena, such as chiral spin-liquid states in spin ice systems or the emergence of new quasiparticles.},
  language  = {en}
}
@article{ChinaBurrowsWangetal.2018,
  author    = {China, Swarup and Burrows, Susannah M. and Wang, Bingbing and Harder, Tristan H. and Weis, Johannes and Tanarhte, Meryem and Rizzo, Luciana V. and Brito, Joel and Cirino, Glauber G. and Ma, Po-Lun and Cliff, John and Artaxo, Paulo and Gilles, Mary K. and Laskin, Alexander},
  title     = {Fungal spores as a source of sodium salt particles in the Amazon basin},
  series = {Nature Communications},
  volume    = {9},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-018-07066-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-222492},
  year      = {2018},
  abstract  = {In the Amazon basin, particles containing mixed sodium salts are routinely observed and are attributed to marine aerosols transported from the Atlantic Ocean. Using chemical imaging analysis, we show that, during the wet season, fungal spores emitted by the forest biosphere contribute at least 30\% (by number) to sodium salt particles in the central Amazon basin. Hydration experiments indicate that sodium content in fungal spores governs their growth factors. Modeling results suggest that fungal spores account for ~69\% (31-95\%) of the total sodium mass during the wet season and that their fractional contribution increases during nighttime. Contrary to common assumptions that sodium-containing aerosols originate primarily from marine sources, our results suggest that locally-emitted fungal spores contribute substantially to the number and mass of coarse particles containing sodium. Hence, their role in cloud formation and contribution to salt cycles and the terrestrial ecosystem in the Amazon basin warrant further consideration.},
  language  = {en}
}
@article{CiuchiDiSanteDobrosavljevićetal.2018,
  author    = {Ciuchi, Sergio and Di Sante, Domenico and Dobrosavljević, Vladimir and Fratini, Simone},
  title     = {The origin of Mooij correlations in disordered metals},
  series = {npj Quantum Materials},
  volume    = {3},
  journal   = {npj Quantum Materials},
  doi       = {10.1038/s41535-018-0119-y},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-223148},
  year      = {2018},
  abstract  = {Sufficiently disordered metals display systematic deviations from the behavior predicted by semi-classical Boltzmann transport theory. Here the scattering events from impurities or thermal excitations can no longer be considered as additive-independent processes, as asserted by Matthiessen's rule following from this picture. In the intermediate region between the regime of good conduction and that of insulation, one typically finds a change of sign of the temperature coefficient of resistivity, even at elevated temperature spanning ambient conditions, a phenomenology that was first identified by Mooij in 1973. Traditional weak coupling approaches to identify relevant corrections to the Boltzmann picture focused on long-distance interference effects such as "weak localization", which are especially important in low dimensions (1D and 2D) and close to the zero-temperature limit. Here we formulate a strong-coupling approach to tackle the interplay of strong disorder and lattice deformations (phonons) in bulk three-dimensional metals at high temperatures. We identify a polaronic mechanism of strong disorder renormalization, which describes how a lattice locally responds to the relevant impurity potential. This mechanism, which quantitatively captures the Mooij regime, is physically distinct and unrelated to Anderson localization, but realizes early seminal ideas of Anderson himself, concerning the interplay of disorder and lattice deformations.},
  language  = {en}
}
@article{KreinbergGrbešićStraussetal.2018,
  author    = {Kreinberg, S{\"o}ren and Grbešić, Tomislav and Strauß, Max and Carmele, Alexander and Emmerling, Monika and Schneider, Christian and H{\"o}fling, Sven and Porte, Xavier and Reitzenstein, Stephan},
  title     = {Quantum-optical spectroscopy of a two-level system using an electrically driven micropillar laser as a resonant excitation source},
  series = {Light: Science \& Applications},
  volume    = {7},
  journal   = {Light: Science \& Applications},
  doi       = {10.1038/s41377-018-0045-6},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229802},
  year      = {2018},
  abstract  = {Two-level emitters are the main building blocks of photonic quantum technologies and are model systems for the exploration of quantum optics in the solid state. Most interesting is the strict resonant excitation of such emitters to control their occupation coherently and to generate close to ideal quantum light, which is of utmost importance for applications in photonic quantum technology. To date, the approaches and experiments in this field have been performed exclusively using bulky lasers, which hinders the application of resonantly driven two-level emitters in compact photonic quantum systems. Here we address this issue and present a concept for a compact resonantly driven single-photon source by performing quantum-optical spectroscopy of a two-level system using a compact high-β microlaser as the excitation source. The two-level system is based on a semiconductor quantum dot (QD), which is excited resonantly by a fiber-coupled electrically driven micropillar laser. We dress the excitonic state of the QD under continuous wave excitation, and trigger the emission of single photons with strong multi-photon suppression (g\(^{(2)}\)(0)=0.02) and high photon indistinguishability (V = 57±9\%) via pulsed resonant excitation at 156 MHz. These results clearly demonstrate the high potential of our resonant excitation scheme, which can pave the way for compact electrically driven quantum light sources with excellent quantum properties to enable the implementation of advanced quantum communication protocols.},
  language  = {en}
}
@article{SoltamovKasperPoshakinskiyetal.2019,
  author    = {Soltamov, V. A. and Kasper, C. and Poshakinskiy, A. V. and Anisimov, A. N. and Mokhov, E. N. and Sperlich, A. and Tarasenko, S. A. and Baranov, P. G. and Astakhov, G. V. and Dyakonov, V.},
  title     = {Excitation and coherent control of spin qudit modes in silicon carbide at room temperature},
  series = {Nature Communications},
  volume    = {10},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-019-09429-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-239149},
  year      = {2019},
  abstract  = {One of the challenges in the field of quantum sensing and information processing is to selectively address and coherently manipulate highly homogeneous qubits subject to external perturbations. Here, we present room-temperature coherent control of high-dimensional quantum bits, the so-called qudits, associated with vacancy-related spins in silicon carbide enriched with nuclear spin-free isotopes. In addition to the excitation of a spectrally narrow qudit mode at the pump frequency, several other modes are excited in the electron spin resonance spectra whose relative positions depend on the external magnetic field. We develop a theory of multipole spin dynamics and demonstrate selective quantum control of homogeneous spin packets with sub-MHz spectral resolution. Furthermore, we perform two-frequency Ramsey interferometry to demonstrate absolute dc magnetometry, which is immune to thermal noise and strain inhomogeneity.},
  language  = {en}
}
@article{TanEloPuskaetal.2018,
  author    = {Tan, Z. B. and Elo, T. and Puska, A. and Sarkar, J. and L{\"a}hteenm{\"a}ki, P. and Duerr, F. and Gould, C. and Molenkamp, L. W. and Nagaev, K. E. and Hakonen, P. J.},
  title     = {Hanbury-Brown and Twiss exchange and non-equilibrium-induced correlations in disordered, four-terminal graphene-ribbon conductor},
  series = {Scientific Reports},
  volume    = {8},
  journal   = {Scientific Reports},
  doi       = {10.1038/s41598-018-32777-5},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240348},
  year      = {2018},
  abstract  = {We have investigated current-current correlations in a cross-shaped conductor made of graphene. The mean free path of charge carriers is on the order of the ribbon width which leads to a hybrid conductor where there is diffusive transport in the device arms while the central connection region displays near ballistic transport. Our data on auto and cross correlations deviate from the predictions of Landauer-B{\"u}ttiker theory, and agreement can be obtained only by taking into account contributions from non-thermal electron distributions at the inlets to the semiballistic center, in which the partition noise becomes strongly modified. The experimental results display distinct Hanbury - Brown and Twiss (HBT) exchange correlations, the strength of which is boosted by the non-equilibrium occupation-number fluctuations internal to this hybrid conductor. Our work demonstrates that variation in electron coherence along atomically-thin, two-dimensional conductors has significant implications on their noise and cross correlation properties.},
  language  = {en}
}
@article{WaldherrLundtKlaasetal.2018,
  author    = {Waldherr, Max and Lundt, Nils and Klaas, Martin and Betzold, Simon and Wurdack, Matthias and Baumann, Vasilij and Estrecho, Eliezer and Nalitov, Anton and Cherotchenko, Evgenia and Cai, Hui and Ostrovskaya, Elena A. and Kavokin, Alexey V. and Tongay, Sefaattin and Klembt, Sebastian and H{\"o}fling, Sven and Schneider, Christian},
  title     = {Observation of bosonic condensation in a hybrid monolayer MoSe2-GaAs microcavity},
  series = {Nature Communications},
  volume    = {9},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-018-05532-7},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-233280},
  year      = {2018},
  abstract  = {Bosonic condensation belongs to the most intriguing phenomena in physics, and was mostly reserved for experiments with ultra-cold quantum gases. More recently, it became accessible in exciton-based solid-state systems at elevated temperatures. Here, we demonstrate bosonic condensation driven by excitons hosted in an atomically thin layer of MoSe2, strongly coupled to light in a solid-state resonator. The structure is operated in the regime of collective strong coupling between a Tamm-plasmon resonance, GaAs quantum well excitons, and two-dimensional excitons confined in the monolayer crystal. Polariton condensation in a monolayer crystal manifests by a superlinear increase of emission intensity from the hybrid polariton mode, its density-dependent blueshift, and a dramatic collapse of the emission linewidth, a hallmark of temporal coherence. Importantly, we observe a significant spin-polarization in the injected polariton condensate, a fingerprint for spin-valley locking in monolayer excitons. Our results pave the way towards highly nonlinear, coherent valleytronic devices and light sources.},
  language  = {en}
}
@article{LeeImhofBergeretal.2018,
  author    = {Lee, Ching Hua and Imhof, Stefan and Berger, Christian and Bayer, Florian and Brehm, Johannes and Molenkamp, Laurens W. and Kiessling, Tobias and Thomale, Ronny},
  title     = {Topolectrical Circuits},
  series = {Communications Physics},
  volume    = {1},
  journal   = {Communications Physics},
  doi       = {10.1038/s42005-018-0035-2},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236422},
  year      = {2018},
  abstract  = {Invented by Alessandro Volta and F{\´e}lix Savary in the early 19th century, circuits consisting of resistor, inductor and capacitor (RLC) components are omnipresent in modern technology. The behavior of an RLC circuit is governed by its circuit Laplacian, which is analogous to the Hamiltonian describing the energetics of a physical system. Here we show that topological insulating and semimetallic states can be realized in a periodic RLC circuit. Topological boundary resonances (TBRs) appear in the impedance read-out of a topolectrical circuit, providing a robust signal for the presence of topological admittance bands. For experimental illustration, we build the Su-Schrieffer-Heeger circuit, where our impedance measurement detects the TBR midgap state. Topolectrical circuits establish a bridge between electrical engineering and topological states of matter, where the accessibility, scalability, and operability of electronics synergizes with the intricate boundary properties of topological phases.},
  language  = {en}
}
@article{KuegelKarolakKroenleinetal.2018,
  author    = {K{\"u}gel, Jens and Karolak, Michael and Kr{\"o}nlein, Andreas and Serrate, David and Bode, Matthias and Sangiovanni, Giorgio},
  title     = {Reversible magnetic switching of high-spin molecules on a giant Rashba surface},
  series = {npj Quantum Materials},
  volume    = {3},
  journal   = {npj Quantum Materials},
  doi       = {10.1038/s41535-018-0126-z},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230866},
  year      = {2018},
  abstract  = {The quantum mechanical screening of a spin via conduction electrons depends sensitively on the environment seen by the magnetic impurity. A high degree of responsiveness can be obtained with metal complexes, as the embedding of a metal ion into an organic molecule prevents intercalation or alloying and allows for a good control by an appropriate choice of the ligands. There are therefore hopes to reach an "on demand" control of the spin state of single molecules adsorbed on substrates. Hitherto one route was to rely on "switchable" molecules with intrinsic bistabilities triggered by external stimuli, such as temperature or light, or on the controlled dosing of chemicals to form reversible bonds. However, these methods constrain the functionality to switchable molecules or depend on access to atoms or molecules. Here, we present a way to induce bistability also in a planar molecule by making use of the environment. We found that the particular "habitat" offered by an antiphase boundary of the Rashba system BiAg2 stabilizes a second structure for manganese phthalocyanine molecules, in which the central Mn ion moves out of the molecular plane. This corresponds to the formation of a large magnetic moment and a concomitant change of the ground state with respect to the conventional adsorption site. The reversible spin switch found here shows how we can not only rearrange electronic levels or lift orbital degeneracies via the substrate, but even sway the effects of many-body interactions in single molecules by acting on their surrounding.},
  language  = {en}
}
@article{LiuWangSatoetal.2019,
  author    = {Liu, Yuhai and Wang, Zhenjiu and Sato, Toshihiro and Hohenadler, Martin and Wang, Chong and Guo, Wenan and Assaad, Fakher F.},
  title     = {Superconductivity from the condensation of topological defects in a quantum spin-Hall insulator},
  series = {Nature Communications},
  volume    = {10},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-019-10372-0},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-237024},
  year      = {2019},
  abstract  = {The discovery of quantum spin-Hall (QSH) insulators has brought topology to the forefront of condensed matter physics. While a QSH state from spin-orbit coupling can be fully understood in terms of band theory, fascinating many-body effects are expected if it instead results from spontaneous symmetry breaking. Here, we introduce a model of interacting Dirac fermions where a QSH state is dynamically generated. Our tuning parameter further allows us to destabilize the QSH state in favour of a superconducting state through proliferation of charge-2e topological defects. This route to superconductivity put forward by Grover and Senthil is an instance of a deconfined quantum critical point (DQCP). Our model offers the possibility to study DQCPs without a second length scale associated with the reduced symmetry between field theory and lattice realization and, by construction, is amenable to large-scale fermion quantum Monte Carlo simulations.},
  language  = {en}
}
@article{OPUS4-31269,
  title     = {Measurement of prompt photon production in √ s(NN) = 8.16 TeV \(p\) Pb collisions with ATLAS},
  series = {Physics letters B},
  volume    = {796},
  journal   = {Physics letters B},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1016/j.physletb.2019.07.031},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312697},
  pages     = {230-252},
  year      = {2019},
  abstract  = {The inclusive production rates of isolated, prompt photons in p Pb collisions at root s(NN) = 8.16 TeV are studied with the ATLAS detector at the Large Hadron Collider using a dataset with an integrated luminosity of 165 nb(-1) recorded in 2016. The cross-section and nuclear modification factor R-p pb are measured as a function of photon transverse energy from 20 GeV to 550 GeV and in three nucleon-nucleon centre-of-mass pseudorapidity regions, (-2.83, -2.02), (-1.84, 0.91), and (1.09, 1.90). The cross-section and R-p pb values are compared with the results of a next-to-leading-order perturbative QCD calculation, with and without nuclear parton distribution function modifications, and with expectations based on a model of the energy loss of partons prior to the hard scattering. The data disfavour a large amount of energy loss and provide new constraints on the parton densities in nuclei. (C) 2019 The Author. Published by Elsevier B.V.},
  language  = {en}
}
@phdthesis{Kappes2024,
  author    = {Kappes, Alexander},
  title     = {High-Redshift Blazars Observed by the International LOFAR Telescope},
  doi       = {10.25972/OPUS-36144},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-361444},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {This work presents the first ILT observations of high redshift blazars and their study in terms of jet evolution, morphology, and interaction with the surrounding medium. Each of these represents a highly topical area of astronomywith a large number of open questions. To better understand Active Galactic Nuclei (AGN) and their fundamental inner workings, new techniques are needed to exploit the full potential of the next generation of radio interferometers. Some of these tools are presented here and applied to one of the latest generation of software radio telescopes. A major focus of the studies presented is on the unification model, where the observed blazars are discussed for their properties to be rotated counterparts of Fanaroff-Riley Class II (FR-II) radio galaxies, when classified as Flat Spectrum Radio Quasars (FSRQs). In addition, multiwavelength information has been included in the analysis. Both studies are feasibility studies that will serve as a basis for future similar studies. The characteristics discussed and their interpretation do not allow conclusions to be drawn for their respective populations. However, by applying them to a larger number of targets, population studies will be possible. The first chapters introduce the necessary topics, AGN, principles of radio observations and ILT, in the necessary depth to provide the reader with a solid knowledge base. They are particularly important for understanding the current limits and influences of uncertainties in the observation, calibration and imaging process. But they also shed light on realistic future improvements. A particular focus is on the development and evolution of the LOw-Frequency ARray (LOFAR)-Very Long Baseline Interferometry (VLBI) pipeline. With the tools at hand, the first study addresses the high redshift blazar S5 0836+710 \$(z=2.218)\$, which has been observed at various wavelengths and resolutions. It has a disrupted one-sided jet with an associated extended region further out. Despite the excellent wavelength coverage, only the additional ILT observations provided a complete picture of the source. With the data, the extended region could be classified as a hotspot moving at slightly relativistic speeds.. With the ILT data it was also possible to extract the flux of the core region of the AGN, and in projection to reveal the mixed counter-hotspot behind it. This also allowed constraints on jet parameters and environmental properties to be modelled, which were previously inconclusive. Technically, this study shows that the ILT can be used as an effective VLBI array for compact sources with small angular scales. However, the detection of faint components beyond redshifts of \$z=2\$ may require the capabilities of the Square Kilometre Array (SKA) to provide a significant number of detections to enable statistical conclusions. The second study uses a much improved calibration pipeline to analyse the high redshift blazar GB1508+5714 \$(z=4.30)\$. The ILT data revealed a previously unseen component in the eastern direction. A spectral index map was generated from the Karl G. Jansky Very Large Array (VLA) data, showing spectral index values of \$-1.2_{-0.2}^{+0.4}\$ for the western component, steeper than \$-1.1\$ for the eastern region, and \$0.023 \pm 0.007\$ for the core. Using the information provided by the ILT observation, as well as multi-wavelength information from other observations ranging from the long radio wavelengths to the \$\gamma\$ regime, four models were developed to interpret the observed flux with different emission origins. This also allowed to test a proposed interaction channel of the electrons provided by the jet, to cool off via inverse compton scattering with the Cosmic Microwave Background (CMB) photons, rather than by the usual synchrotron emission. This is referred to as cmb quenching in the literature, which could be shown in the study, to be necessary in any case. Finally, one of the four models was considered in which the hotspots in the detected components are unresolved and mixed by the lobe emission, with the X-ray emission coming from the lobes and partially mixed by the bright core region. The results of this preferred model are consistent with hotspots in a state of equipartition and lobes almost so. The study shows that high redshift blazars can be studied with the ILT, and expanding the sample of high redshift blazars resolved at multiple frequencies will allow a statistical study of the population. Finally, this work successfully demonstrates the powerful capabilities of the ILT to address questions that were previously inaccessible. The current state of the LOFAR-VLBI pipeline, when properly executed, allows work on the most challenging objects and will only improve in the future. In particular, this gives a glimpse of the possibilities that SKA will bring to astronomy.},
  subject      = {Blazar},
  language  = {en}
}
@article{ŽutićMatosAbiagueScharfetal.2019,
  author    = {Žutić, Igor and Matos-Abiague, Alex and Scharf, Benedikt and Dery, Hanan and Belashchenko, Kirill},
  title     = {Proximitized materials},
  series = {Materials Today},
  volume    = {22},
  journal   = {Materials Today},
  doi       = {10.1016/j.mattod.2018.05.003},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-233972},
  pages     = {85-107},
  year      = {2019},
  abstract  = {Advances in scaling down heterostructures and having an improved interface quality together with atomically thin two-dimensional materials suggest a novel approach to systematically design materials. A given material can be transformed through proximity effects whereby it acquires properties of its neighbors, for example, becoming superconducting, magnetic, topologically nontrivial, or with an enhanced spin-orbit coupling. Such proximity effects not only complement the conventional methods of designing materials by doping or functionalization but also can overcome their various limitations. In proximitized materials, it is possible to realize properties that are not present in any constituent region of the considered heterostructure. While the focus is on magnetic and spin-orbit proximity effects with their applications in spintronics, the outlined principles also provide a broader framework for employing other proximity effects to tailor materials and realize novel phenomena.},
  language  = {en}
}
@article{FaberHudecMalinskyetal.2018,
  author    = {Faber, T. and Hudec, M. and Malinsk{\´y}, M. and Meinzinger, P. and Porod, W. and Staub, F.},
  title     = {A unified leptoquark model confronted with lepton non-universality in B-meson decays},
  series = {Physics Letters B},
  volume    = {787},
  journal   = {Physics Letters B},
  doi       = {10.1016/j.physletb.2018.10.051},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-227419},
  pages     = {159-166},
  year      = {2018},
  abstract  = {The anomalies in the B-meson sector, in particular R-K(*) and R-D(*), are often interpreted as hints for physics beyond the Standard Model. To this end, leptoquarks or a heavy Z' represent the most popular SM extensions which can explain the observations. However, adding these fields by hand is not very satisfactory as it does not address the big questions like a possible embedding into a unified gauge theory. On the other hand, light leptoquarks within a unified framework are challenging due to additional constraints such as lepton flavor violation. The existing accounts typically deal with this issue by providing estimates on the relevant couplings. In this letter we consider a complete model based on the SU(4)(C) circle times SU(2)(L) circle times U(1) R gauge symmetry, a subgroup of SO(10), featuring both scalar and vector leptoquarks. We demonstrate that this setup has, in principle, all the potential to accommodate R-K(*) and R-D(*) while respecting bounds from other sectors usually checked in this context. However, it turns out that K-L -> e(+/-)mu(-/+) severely constraints not only the vector but also the scalar leptoquarks and, consequently, also the room for any sizeable deviations of R-K(*) from 1. We briefly comment on the options for extending the model in order to conform this constraint. Moreover, we present a simple criterion for all-orders proton stability within this class of models.},
  language  = {en}
}
@phdthesis{Dusel2024,
  author    = {Dusel, Marco},
  title     = {Exziton-Polariton-Kondensation in organischen Halbleiter-Mikrokavit{\"a}ten mit hemisph{\"a}rischen Potentiallandschaften},
  doi       = {10.25972/OPUS-37055},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-370554},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {Exziton-Polaritonen sind hybride Quasiteilchen, die entstehen durch die starke Kopplung zwischen Halbleiter-Exzitonen und Mikrokavit{\"a}tsphotonen in einem optischen Resonator. Aufgrund ihres bosonischen Charakters k{\"o}nnen die Polaritonen Kondensate ausbilden. In dieser Arbeit ist der emittierende organische Halbleiter das fluoreszierende Protein mCherry. Um einen r{\"a}umlichen Einschluss zu generieren wurden hemisph{\"a}rische Potentiale genutzt. Durch die Variation der Potentiallandschaft (Linse, Molek{\"u}l, Kette, Su-Schrieffer-Heeger-Kette und Honigwaben-Gitter) konnten Eigenschaften wie beispielsweise topologisch nicht-triviale Defekte experimentell bei Umgebungstemperatur demonstriert werden. Zusammengefasst besch{\"a}ftigt sich diese Arbeit mit der Exziton-Polartion Kondensation in unterschiedlichen Potentiallandschaften mit dem organischen Halbleiter mCherry.},
  subject      = {Exziton-Polariton},
  language  = {de}
}
@phdthesis{Rode2024,
  author    = {Rode, Stefan},
  title     = {Automated resummation of electroweak Sudakov logarithms in diboson production},
  doi       = {10.25972/OPUS-37106},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-371060},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {The present thesis is concerned with the automated computation of integrated and differential cross sections of diboson production in proton-proton and electron-positron collisions at very high energies, including a resummation of electroweak Sudakov logarithms to all orders in the fine-structure constant using soft-collinear effective theory. The search for new physics at future colliders such as the FCC-hh or the CLIC requires precise predictions for scattering cross sections from the theoretical high-energy physics com- munity. Electroweak Sudakov logarithms, which currently limit the accuracy of predictions in the high-energy tails of differential distributions for LHC-like energies, are known to destroy the convergence behaviour of the fixed-order perturbative series, once sufficiently high energies are considered. To resum these large corrections, soft-collinear effective theory has been applied to simple processes, which permits analytic calculations. Within this work, we present an automated computation within a Monte Carlo integration framework, thus facilitating the computation of fully differential cross section to complicated processes. This requires the use of the Catani- Seymour subtraction algorithm to treat the occurring infrared divergences. The machinery is applied to all diboson processes with intermediate weak gauge bosons, including the photon- induced W+ W- -production channel. To this end we carefully study the validity of the necessary assumptions such as the double- pole approximation and estimate the order of magnitude of neglected effects. Especially the non-doubly-resonant contributions turn out to be sizeable in several interesting phase-space regions. For lepton collisions at 3 TeV we obtain the integrated cross sections of W-pair and Z-pair production to be shifted by more than 20\% with respect to the Born value, owing to the resum- mation of the leading-logarithmic corrections These effects are partly cancelled by subleading effects. For proton-proton collisions at √ s = 100 TeV we observe sizeable resummation effects in the high-energy tails, while the integrated cross sections are dominated by interactions, for which soft-collinear effective theory is not applicable.},
  language  = {en}
}
@phdthesis{Liu2024,
  author    = {Liu, Yang},
  title     = {Predictions for Composite Higgs Models Using Gauge/Gravity Duality},
  doi       = {10.25972/OPUS-37083},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-370833},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {This thesis is dedicated to construct a non-abelian holographic dynamical minimal composite Higgs model. We first build a non-abelian bottom-up AdS/YM model that can explain the QCD meson spectrum well. The model is made non-abelian by considering non-abelian DBI action in the top-down model. We then change the dual theory from the QCD to the minimal composite Higgs model U (4)/Sp(4). By adding a second explicit U (4) → Sp(4) breaking through the NJL interaction at the boundary, we managed to construct a composite Higgs phase and a technicolor phase in this model. The transition between the two phases is also realized, which is controlled by the NJL coupling. This thesis is based on the works [1, 2].},
  subject      = {Higgs-Modell},
  language  = {en}
}
@article{KampfBauerReiter2018,
  author    = {Kampf, Thomas and Bauer, Wolfgang Rudolf and Reiter, Theresa},
  title     = {Improved post-processing strategy for MOLLI based tissue characterization allows application in patients with dyspnoe and impaired left ventricular function},
  series = {Zeitschrift f{\"u}r Medizinische Physik},
  volume    = {28},
  journal   = {Zeitschrift f{\"u}r Medizinische Physik},
  doi       = {10.1016/j.zemedi.2017.07.003},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-325481},
  pages     = {25-35},
  year      = {2018},
  abstract  = {Contrast and non-contrast MRI based characterization of myocardium by T1-mapping will be of paramount importance to obtain biomarkers, e.g. fibrosis, which determines the risk of heart failure patients. T1-mapping by the standard post-processing of the modified look-locker inversion recovery (MOLLI) lacks of accuracy when trying to reduce its duration, which on the other hand, is highly desirable in patients with heart failure. The recently suggested inversion group fitting (IGF) technique, which considers more parameters for fitting, has a superior accuracy for long T1 times despite a shorter duration. However, for short T1 values, the standard method has a superior precision. A conditional fitting routine is proposed which ideally takes advantage of both algorithms. Materials and methods All measurements were performed on a 1.5 T clinical scanner (ACHIEVA, Philips Healthcare, The Netherlands) using a MOLLI 5(n)3(n)3 prototype with n(heart beats) being a variable waiting time between inversion experiments. Phantom experiments covered a broad range of T1 times, waiting times and heart rates. A saturation recovery experiment served as a gold standard for T1 measurement. All data were analyzed with the standard MOLLI, the IGF fit and the conditional fitting routine and the obtained T1 values were compared with the gold standard. In vivo measurements were performed in a healthy volunteer and a total of 34 patients with normal findings, dilative cardiomyopathy and amyloidosis. Results Theoretical analysis and phantom experiments provided a threshold value for an apparent IGF determining processing with IGF post processing for values above, or switching to the standard technique for values below. This was validated in phantoms and patients measurements. A reduction of the waiting time to 1 instead of 3 heart beats between the inversion experiments showed reliable results. The acquisition time was reduced from 17 to 13 heart beats. The in vivo measurements showed ECV values between 25\% (18-33\%; SD 0.03) in the healthy, 30\% (22-40\%; SD 0.04) in patients with DCM and 45\% (30-60\%; SD 0.9) in patients with amyloidosis. Conclusion The adopted post-processing algorithm determines long T1 values with high accuracy and short T1 values while maintaining a high precision. Based on reduction of waiting time, and independence of heart rate, it shortens breath hold duration and allows fast T1-mapping, which is frequently a prerequisite in patients with cardiac diseases.},
  language  = {en}
}
@article{KampfReiterBauer2018,
  author    = {Kampf, Thomas and Reiter, Theresa and Bauer, Wolfgang Rudolf},
  title     = {An analytical model which determines the apparent T1 for Modified Look-Locker Inversion Recovery - Analysis of the longitudinal relaxation under the influence of discontinuous balanced (classical MOLLI) and spoiled gradient echo readouts},
  series = {Zeitschrift f{\"u}r Medizinische Physik},
  volume    = {28},
  journal   = {Zeitschrift f{\"u}r Medizinische Physik},
  doi       = {10.1016/j.zemedi.2017.07.004},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-325498},
  pages     = {150-157},
  year      = {2018},
  abstract  = {Quantitative nuclear magnetic resonance imaging (MRI) shifts more and more into the focus of clinical research. Especially determination of relaxation times without/and with contrast agents becomes the foundation of tissue characterization, e.g. in cardiac MRI for myocardial fibrosis. Techniques which assess longitudinal relaxation times rely on repetitive application of readout modules, which are interrupted by free relaxation periods, e.g. the Modified Look-Locker Inversion Recovery = MOLLI sequence. These discontinuous sequences reveal an apparent relaxation time, and, by techniques extrapolated from continuous readout sequences, a putative real T1 is determined. What is missing is a rigorous analysis of the dependence of the apparent relaxation time on its real partner, readout sequence parameters and biological parameters as heart rate. This is provided in this paper for the discontinuous balanced steady state free precession (bSSFP) and spoiled gradient echo readouts. It turns out that the apparent longitudinal relaxation rate is the time average of the relaxation rates during the readout module, and free relaxation period. Knowing the heart rate our results vice versa allow to determine the real T1 from its measured apparent partner.},
  language  = {en}
}
@article{OPUS4-31409,
  title     = {Electron and photon energy calibration with the ATLAS detector using 2015-2016 LHC proton-proton collision data},
  series = {Journal of Instrumentation},
  volume    = {14},
  journal   = {Journal of Instrumentation},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1088/1748-0221/14/03/P03017},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-314093},
  pages     = {1-58},
  year      = {2019},
  abstract  = {This paper presents the electron and photon energy calibration obtained with the ATLAS detector using about 36 fb(-1) of LHC proton-proton collision data recorded at root s = 13 TeV in 2015 and 2016. The different calibration steps applied to the data and the optimization of the reconstruction of electron and photon energies are discussed. The absolute energy scale is set using a large sample of Z boson decays into electron-positron pairs. The systematic uncertainty in the energy scale calibration varies between 0.03\% to 0.2\% in most of the detector acceptance for electrons with transverse momentum close to 45 GeV. For electrons with transverse momentum of 10 GeV the typical uncertainty is 0.3\% to 0.8\% and it varies between 0.25\% and 1\% for photons with transverse momentum around 60 GeV. Validations of the energy calibration with J/psi -> e(+)e(-) decays and radiative Z boson decays are also presented.},
  language  = {en}
}
@phdthesis{Franken2024,
  author    = {Franken, Robert},
  title     = {Precision Predictions for \(\mathrm W^+ \mathrm W^-\) Scattering at the LHC},
  doi       = {10.25972/OPUS-36944},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-369445},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {In this thesis we examine the vector boson scattering (VBS) process \(\mathrm p \mathrm p \to \mathrm e^+ \nu_\mathrm e\mu^-\bar\nu_\mu\mathrm j\mathrm j +X\) (short: \(\mathrm W^+\mathrm W^-\) scattering) at NLO accuracy in two experimental setups by performing a Monte Carlo analysis of a \(13\,\mathrm{TeV}\) LHC run. \(\mathrm W^+\mathrm W^-\) scattering shows similarities and differences compared to the scattering of other vector bosons. We present a detailed description of the types of appearing subprocesses and background processes. We give insight into our code which solves the problems we are faced within \(\mathrm W^+\mathrm W^-\) scattering. This is especially the presence of the Higgs-boson resonance in the fiducial phase-space region. Particular attention is dedicated to the permutation of resonances. The integrated signal cross section at LO \(\mathcal O(\alpha^6)\) amounts to \(2.6988(3)\,\mathrm{fb}\) and \(1.5322(2)\,\mathrm{fb}\), respectively, in the two experimental setups. The LO QCD-induced background of \(\mathcal O(\alpha_\mathrm s^2\alpha^4)\) amounts to \(6.9115(9)\,\mathrm{fb}\) and \(1.6923(3)\,\mathrm{fb}\). The EW corrections to the signal are \(-11.4\\%\) and \(-6.7\\%\), the QCD corrections amount to \(-5.2\\%\) and \(-23.0\\%\). The EW corrections to the background are \(-8.3\\%\) and \(-5.3\\%\), the QCD corrections amount to \(-30.3\\%\) and \(-77.6\\%\). Our results for the QCD corrections and the QCD-induced background include a large uncertainty from varying the renormalisation and factorisation scale, and we discuss improvements for future calculations. We show the differential cross sections with unique features of \(\mathrm W^+\mathrm W^-\) scattering compared to other VBS processes and investigate in particular the subprocess of Higgs-boson production by using a modified version of our setups.},
  subject      = {W-Boson},
  language  = {en}
}
@phdthesis{Baumann2024,
  author    = {Baumann, Johannes},
  title     = {Induced Superconductivity in HgTe Quantum Point Contacts},
  doi       = {10.25972/OPUS-36940},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-369405},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {In this thesis, the Josephson effect in mercury telluride based superconducting quantum point contacts (SQPCs) is studied. Implementing such confined structures into topological superconductors has been proposed as a means to detect and braid Majorana fermions. For the successful realization of such experiments though, coherent transport across the constriction is essential. By demonstrating the Josephson effect in a confined topological system, the presented experiments lay the foundation for future quantum devices that can be used for quantum computation. In addition, the experiments also provide valuable insights into the behavior of the Josephson effect in the low-channel limit (N<20). Due to the confinement of the weak link, we can also study the Josephson effect in a topological insulator, where the edge modes interact. In conclusion, this thesis discusses the fabrication of, and low-temperature measurements on mercury telluride quantum point contacts embedded within Josephson junctions. We find that the merging of the currently used fabrication methods for mercury telluride quantum point contacts and Josephson junctions does not yield a good enough device quality to resolve subbands of the quantum point contact as quantization effects in the transport properties. As we attribute this to the long dry etching time that is necessary for a top-contact, the fabrication process was adapted to reduce the defect density at the superconductor-semiconductor interface. Employing a technique that involves side contacting the mercury telluride quantum well and reducing the size of the mercury telluride mesa to sub-micrometer dimensions yields a quantized supercurrent across the junction. The observed supercurrent per mode is in good agreement with theoretical predictions for ballistic, one-dimensional modes that are longer than the Josephson penetration depth. Moreover, we find that oscillatory features superimpose the plateaus of the supercurrent and the conductance. The strength of these oscillatory features are sample-dependent and complicate the identification of plateaus. We suggest that the oscillatory features originate mainly from local defects and the short gate electrode. Additionally, resonances are promoted within the weak link if the transparency of the superconductor-HgTe interface differs from one. Furthermore, the research explores the regimes of the quantum spin Hall effect and the 0.5 anomaly. Notably, a small yet finite supercurrent is detected in the QSH regime. In samples fabricated from thick mercury telluride quantum wells, the supercurrent appears to vanish when the quantum point contact is tuned into the regime of the 0.5 anomaly. For samples fabricated from thin mercury telluride quantum wells, the conductance as well as the supercurrent vanish for strong depopulation. In these samples though, the supercurrent remains detectable even for conductance values significantly below 2 e²/h. Numerical calculation reproduce the transport behavior of the superconducting quantum point contacts. Additionally, the topological nature of the weak link is thoroughly investigated using the supercurrent diffraction pattern and the absorption of radio frequency photons. The diffraction pattern reveals a gate independent, monotonous decay of \$I_\text{sw}(B)\$, which is associated with the quantum interference of Andreev bound states funneled through the quantum point contact. Interestingly, the current distribution in the weak link appears unaffected as the quantum point contact is depleted. In the RF measurements, indications of a 4π periodic supercurrent are observed as a suppression of odd Shapiro steps. The ratio of the 4π periodic current to the 2π periodic current appears to decrease for smaller supercurrents, as odd Shapiro steps are exclusively suppressed for large supercurrents. Additionally, considering the observation that the supercurrent is small when the bulk modes in the quantum point contact are fully depleted, we suggest that the re-emerging of odd Shapiro steps is a consequence of the group velocity of the edge modes being significantly suppressed when the bulk modes are absent. Consequently, the topological nature of the superconducting quantum point contact is only noticeable in the transport properties when bulk modes are transmitted through the superconducting quantum point contact. The shown experiments are the first demonstration of mercury telluride superconducting quantum point contacts that exhibit signatures of quantization effects in the conductance as well as the supercurrent. Moreover, the experiments suggest that the regime of interacting topological edge channels is also accessible in mercury telluride superconducting quantum point contacts. This is potentially relevant for the realization of Majorana fermions and their application in the field of quantum computation.},
  subject      = {Topologischer Isolator},
  language  = {en}
}
@phdthesis{Dorband2024,
  author    = {Dorband, Moritz},
  title     = {Geometric Phases and Factorisation in Quantum Physics and Gravity},
  doi       = {10.25972/OPUS-37093},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-370937},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {In this thesis I explore the interplay of geometry and quantum information theory via the holographic principle, with a specific focus on geometric phases in quantum systems like two interacting qubits, and how they relate to entanglement measures and Hilbert space factorisation. I establish geometric phases as an indicator for Hilbert space factorsiation, both in an abstract sense using von Neumann operator algebras as well as applied to the eternal black hole within the AdS/CFT correspondence. For the latter case I show that geometric phases allow to diagnose non-factorisation from a boundary point of view. I also introduce geometric quantum discord as a second geometric measure for non-factorisation and reveals its potential implications for the study of black hole microstates.},
  subject      = {AdS-CFT-Korrespondenz},
  language  = {en}
}
@article{OPUS4-31382,
  title     = {Dijet azimuthal correlations and conditional yields in \({pp}\) and \(p\) + Pb collisions at √S-NN=5.02 TeV with the ATLAS detector},
  series = {Physical Review C},
  volume    = {100},
  journal   = {Physical Review C},
  number    = {3},
  organization    = {The ATLAS Collaboration},
  doi       = {10.1103/PhysRevC.100.034903},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-313823},
  pages     = {1-24},
  year      = {2019},
  abstract  = {This paper presents a measurement of forward-forward and forward-central dijet azimuthal angular correlations and conditional yields in proton-proton (pp) and proton-lead (p + Pb) collisions as a probe of the nuclear gluon density in regions where the fraction of the average momentum per nucleon carried by the parton entering the hard scattering is low. In these regions, gluon saturation can modify the rapidly increasing parton distribution function of the gluon. The analysis utilizes 25 pb(-1) of pp data and 360 mu b(-1) of p + Pb data, both at root S-NN = 5.02 TeV, collected in 2015 and 2016, respectively, with the ATLAS detector at the Large Hadron Collider. The measurement is performed in the center-of-mass frame of the nucleon-nucleon system in the rapidity range between -4.0 and 4.0 using the two highest transverse-momentum jets in each event, with the highest transverse-momentum jet restricted to the forward rapidity range. No significant broadening of azimuthal angular correlations is observed for forward-forward or forward-central dijets in p + Pb compared to pp collisions. For forward-forward jet pairs in the proton-going direction, the ratio of conditional yields in p + Pb collisions to those in pp collisions is suppressed by approximately 20\%, with no significant dependence on the transverse momentum of the dijet system. No modification of conditional yields is observed for forward-central dijets.},
  language  = {en}
}