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Gas Quenching under Ambient Conditions for Efficient and Stable Wide-Bandgap Perovskite Solar Cells with Surface Passivation
No full textWide-bandgap perovskite solar cells play a key role in tandem solar cells, which aim to overcome the Shockley–Queisser limit for single-junction solar cells. In this work, we develop and optimize a gas quenching method under ambient conditions for the fabrication of wide-bandgap (1.77 eV) perovskite films. To improve the performance of PSCs, three different organic spacer cations, including aromatic amino molecules (PEAI), aliphatic amino with long alkyl chain molecules (OAI), and short alkyl chain molecules (BAI), are applied and investigated as surface passivation materials. As a result, the 2D perovskite layers form on top of the 3D perovskite films. The n-i-p devices with PEAI passivation exhibit the highest photovoltaic performance with a champion power conversion efficiency (PCE) of 16.26% along with a high Voc of 1.21 V, exceeding the control device (PCE = 13.42%, Voc = 1.15 V), and maintaining 88% of its initial PCE after 120 min of continuous illumination under a nitrogen atmosphere at room temperature. This work offers a guide for the fabrication of wide-bandgap PSCs under ambient conditions and the choice of organic spacer cations for passivation
Dispersion relation for the linear theory of relativistic Rayleigh–Taylor instability in a magnetized medium revisited
No full textThe Rayleigh–Taylor instability (RTI) arises at the interface between two fluids of different densities, notably when a heavier fluid lies above a lighter one in an effective gravitational field. In astrophysical systems with high velocities, relativistic corrections are necessary. We investigate the linear theory of the relativistic Rayleigh-Taylor instability (R-RTI) in a magnetized medium, where fluids can move with relativistic velocities. We chose an "intermediate frame" in which the fluids on each side of the interface move in opposite directions with identical Lorentz factors and derive the new dispersion relation of the R-RTI. This symmetry facilitates analytical derivations and the study of relativistic effects on the dynamics of instabilities. We find that the instability is activated when the Atwood number = , where and are densities measured in the rest of the fluids. The relativistic effect is mostly contained in the Lorentz transformation of the effective acceleration , which, combined with time dilation, leads to a much slower growth of instability (), and a slightly elongated length of the unstable patch, due to weaker in the intermediate frame. Taking time dilation into account, when viewed in the rest frame of the medium, we expect the instability to grow at a much reduced rate. The analytical results should guide further explorations of instability in systems such as microquasars (QSOs), Active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and radio pulsars (PSRs), where the apparent stability of the jet can be attributed to either the intrinsic stability (e.g. the Atwood number) or the much prolonged duration through which R-RTI can grow
Discovery of high-temperature charge order and time-reversal symmetry-breaking in the kagome superconductor YRuSi
No full textIdentifying high-temperature unconventional charge order and superconductivity in kagome systems is crucial for understanding frustrated, correlated electrons and enabling future quantum technologies. Here, we report that the kagome superconductor YRuSi hosts an exceptional interplay of charge order, magnetism, and superconductivity, revealed through a comprehensive suite of muon spin rotation (μSR), magnetotransport, X-ray diffraction, and density functional theory (DFT). We identify a high-temperature charge-ordered state with propagation vector (1/2,0,0) and a record onset temperature of 800 K, unprecedented in kagome systems and quantum materials more broadly. μSR measurements further reveal time-reversal symmetry-breaking below 25 K and field-induced magnetism near 90 K, features mirrored in the magnetoresistance, which reaches 45% at low temperatures. Band-structure calculations show two van Hove singularities near the Fermi level, including one within a flat band. At low temperatures, YRuSi becomes superconducting below Tc = 3.4 K with either two full isotropic gaps or an anisotropic nodeless gap. These results establish YRuSi as a prime platform for studying correlated kagome physics
Inducing Riesz Bases in via Composition Operators
No full textLet Ch be a composition operator mapping L2(1) into L2(2) for some open sets1, 2 ⊆ Rn. We characterize the mappings h that transform Riesz bases of L2(1)into Riesz bases of L2(2). Restricting our analysis to differentiable mappings, wedemonstrate that mappings h that preserve Riesz bases have Jacobian determinantsthat are bounded away from zero and infinity. We discuss implications of these resultsfor approximation theory, highlighting the potential of using bijective neural networksto construct Riesz bases with favorable approximation properties
Full event interpretation with machine-learning-based particle-flow reconstruction in the CMS detector
No full textThe particle-flow (PF) algorithm constructs a global description of each particle collision by producing a comprehensive list of final-state particles, and is central to event reconstruction in the CMS experiment at the CERN LHC. The existing PF implementation relies on physics-motivated heuristics and assumptions that can be replaced by machine-learning (ML) models trained directly on simulated data and naturally suited to modern graphics processing units (GPUs). A state-of-the-art ML-based PF (MLPF) reconstruction algorithm, implemented within the CMS software framework, is presented. The MLPF algorithm performs a learnable full-event reconstruction on GPUs, generalizes across detector conditions and collision energies, and replaces multiple modular reconstruction steps with a single unified model. Physics performance comparable to standard PF reconstruction is achieved in both simulation and data, with improved jet energy resolution and inference time. In simulated top quark-antiquark events under LHC Run-3 (20232024) conditions, the jet energy resolution improves by 1020% for jets with transverse momentum between 30100 GeV. Inference time is evaluated using simulated multijet events, with a median of 20 ms per event on an Nvidia L4 GPU, compared to approximately 110 ms for the standard CMS PF reconstruction
Complete Series of 1,2‐Bis(trihalogenosilyl)benzenes (F, Cl, Br, I): A Platform for Cooperating Lewis‐Acidic Sites in Close Quarters
No full text1,2-Bis(trihalogenosilyl)benzenes are versatile synthetic building blocks and represent a unique class of ditopic Lewis acids. Building on the recently reported compound 1,2-(Cl3Si)2C6H2Me2 (1Cl; Me groups in 4,5-positions), the practical synthetic access to its sixfold fluorinated (1F), brominated (1Br), and iodinated (1I) congeners is disclosed. Compound 1F is obtained via Cl/F exchange on 1Cl using SbF3 (71%). The synthesis of 1Br involves a [4 + 2]-cycloaddition reaction between Br3SiC≡CSiBr3 and 2,3-dimethyl-1,3-butadiene to furnish the corresponding 1,4-cyclohexadiene, which is subsequently dehydrogenated and aromatized using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (overall 59%). Compound 1I is formed through H/I exchange on 1,2-(H3Si)2-C6H2Me2 with BI3 (32%). All species 1F−1I are comprehensively characterized by NMR spectroscopy, X-ray crystallography, elemental analysis, and high-resolution mass spectrometry. Moreover, adducts of 1F with either 1 equiv. or 2 equiv. of F− are shown to form an inverse chelate featuring a Si−(μ-F)−Si′ bridge or a mixed bridging/terminal coordination motif, respectively
From cabinets to collectomics: discovering females and primary larvae of Strepsiptera in a historical collection
No full textNatural history collections house material from centuries of collecting efforts. In the Phyletisches Museum Jena (PMJ), ca. 1 Mio specimens are deposited, some of them dating back as far as the 17th century. Modern imaging techniques have the potential to gain new insights from this historical material. However, a large part of the PMJ insect collection has not been revised by scientists in recent times. We screened the entire Auchenorrhyncha collection and found several specimens parasitized by two different species of the genus Halictophagus (Halictophagidae, Strepsiptera) that had previously been overlooked. These historical findings represent the only evidence to date of the occurrence of these two species in Germany and therefore suggest, at least historically, a larger distribution area than was previously known. In addition, hitherto unknown females and primary larvae were morphologically documented using state-of-the-art techniques such as synchrotron-radiation-based X-ray µCT and scanning electron microscopy. The data generated in this study cover the field of collectomics and can be seamlessly used as a basis for the emerging discipline of museomics. In taxonomic and systematic research and in the context of environmental change, pinned insects may play an outstanding role in the near future, as their DNA is not damaged by formalin fixation and thus can yield remarkable results even after more than 100 years. Our results underpin the value of historical material for modern research questions, especially for species that are difficult to find in nature
Warm Start of Variational Quantum Algorithms for Quadratic Unconstrained Binary Optimization Problems
No full textVariational Quantum Eigensolver (VQE) is widely used in near-term hardware. However, their performances remain limited by the poor trainability and are dependent on random parameter initialization. In this work, we propose a warm start method inspired by imaginary time evolution, allowing for determining initial parameters that prioritize lower energy states in a resource-efficient way. Using classical simulations, we demonstrate that this warm start method significantly improves the success rate and reduces the number of iterations required for the convergence of VQE. The numerical results also indicate that the warm start approach effectively mitigates statistical errors arising from a finite number of measurements, and to a certain extent alleviates the effect of barren plateaus
Ultrafast recovery dynamics of dimer stripes in
No full textThe transition metal dichalcogenide IrTedisplays a remarkable series of first-order phase transitions below room temperature, involving lattice displacements as large as 20% of the initial bond length. This is nowadays understood as the result of strong electron-phonon coupling leading to the formation of local multicenter dimers that arrange themselves into one-dimensional stripes. In this work, we study the out-of-equilibrium dynamics of these dimers and track the time evolution of their population following an infrared photoexcitation using free-electron lased-based time-resolved x-ray photoemission spectroscopy. First, we observe that the dissolution of dimers is driven by the transfer of energy from the electronic subsystem to the lattice subsystem, in agreement with previous studies. Second, we observe a surprisingly fast relaxation of the dimer population on the timescale of a few picoseconds. By comparing our results to published ultrafast electron diffraction and angle-resolved photoemission spectroscopy data, we reveal that the long-range order needs tens of picoseconds to recover, while the local dimer distortion recovers on a short timescale of a few picoseconds
X-ray standing wave method to study magnetism in crystals with site selectivity
No full textWe report a new method for studying magnetism at the atomic level with site selectivity. It is based on thecombination of the site-selective diffraction-based x-ray standing wave (XSW) technique and x-ray magneticcircular dichroism (XMCD), which provides the magnetic sensitivity. The use of the standing wave resultingfrom an interference between the incoming and the Bragg reflected electromagnetic waves ensures that the phaseinformation is not lost and thus brings information about the magnetism at a given site directly. In the paper, weprovide the theoretical foundations of such a method based on the dynamical theory of x-ray diffraction andtime-dependent perturbation theory. By means of computer simulations, the principle of the method is thuspresented in a rather accessible way. Finally, we demonstrate the results of a proof-of-principle experiment onsingle-crystalline yttrium-iron-garnet (YIG, YFeO). We show data exhibiting a clear variation in the XMCDsignal caused by the standing wave. A comparison with theoretical functions illustrates that the established theoryreliably describes the phenomena involved and allows to extract useful information about the magnetic momentsin YIG