Sharp Transition Research Articles

Weighted Median Filtering for Terrain and Contour Generalization

Abstract. When working with terrain elevation data, as in image processing, it is often desirable to smooth the data, for purposes such as map generalization or removal of noise. Median filtering is one common technique that can be used for this purpose. It differs from linear filtering techniques like local averaging or Gaussian blurring by its ability to smooth while retaining sharp edges in an image. When applied to elevation data, this means that median filtering can better preserve steep slopes and cliffs while otherwise reducing noise or excessive detail in the terrain. However, median filtering as typically applied can also introduce new artifacts, such as lopping off the tops of peaks and ridges to create flat plateaus that don’t exist in the original landscape. A lesser known technique, a weighted median filter, can reduce or eliminate these artifacts. This method shows promise as a way to generalize digital elevation models, as well as their associated contour lines. It can also be used to smooth hillshaded images, preserving the sharp transition in shading that occurs across ridges. And due to its ability to retain discontinuities in the data, it can be used to locate latent terracing effects hidden in elevation data, which may represent real terrain features or may indicate artifacts of the processing methods used to generate the data.

Capturing the Variability of the Nocturnal Boundary Layer through Localized Perturbation Modeling

Abstract A single-column model is used to investigate regime transitions within the stable atmospheric boundary layer, focusing on the role of small-scale fluctuations in wind and temperature dynamics and of turbulence intermittency as triggers for these transitions. Previous studies revealed abrupt near-surface temperature inversion transitions within a limited wind speed range. However, representing these transitions in numerical weather prediction (NWP) and climate models is a known difficulty. To shed light on boundary layer processes that explain these abrupt transitions, the Ekman layer height and its correlation with regime shifts are analyzed. A sensitivity study is performed with several types of perturbations of the wind and temperature tendencies, as well as with the inclusion of intermittent turbulent mixing through a stochastic stability equation. The effect of small fluctuations of the dynamics on regime transitions is thereby quantified. The combined results for all tested perturbation types indicate that small-scale phenomena can drive persistent regime transitions from very to weakly stable regimes, but for the opposite direction, no evidence of persistent regime transitions was found. The inclusion of intermittency prevents the model from getting trapped in the very stable regime, thus preventing the so-called ”runaway cooling”, an issue for commonly used short-tail stability functions. The findings suggest that using stochastic parameterizations of boundary layer processes, either through stochastically perturbed tendencies or parameters, is an effective approach to represent sharp transitions in the boundary layer regimes and is, therefore, a promising avenue to improve the representation of stable boundary layers in NWP and climate models.

Capturing Broadband Spectral Characteristics of Moderate-Size Earthquakes Using Nearby Recordings: A Case Study of 42 Mw 4.0–5.4 Ridgecrest Earthquakes

ABSTRACT Characterizing the information in earthquake source spectra requires three measures: seismic moment M0, apparent stress σa, and stress parameter ΔσB. We estimate σa and ΔσB for 42 Ridgecrest, California, earthquakes (4.0≤Mw≤5.4), using three-component records within 50 km to minimize path effects. We analyze the data in both the time and frequency domains. We account for the depth dependence of source velocity and density and calibrate the results using observations at a rock site. Time-domain analysis for σa reveals significant apparent crustal attenuation (∝r−1.6, in which r is the centroid distance) and large site amplifications. In the frequency domain, we estimate near-surface impedance as a function of frequency at each station. We conduct a grid search with F-tests to constrain a frequency-dependent crustal Q model (Q(f)=q0fα) and site attenuation constant κ0 for each station, assuming a ω−2 model. The global best model has q0=60, α=0.675, with κ0 ranging from 0.01 to 0.05 s. σa and ΔσB were estimated using corrected observations. The σa values from both time- and frequency-domain analyses are in excellent agreement, ranging from 0.09 to 2.7 MPa with a geometric mean of 0.59 MPa. ΔσB ranges from 0.27 to 6.9 MPa with a geometric mean of 1.8 MPa. The ratio of ΔσB and σa (∼3.0) suggests the source spectrum in this magnitude range is close to a single-corner spectral model. We find both σa and ΔσB increase quickly with centroid depth that cannot be explained with depth-dependent crustal attenuation. Geometric mean values for σaF and ΔσB for earthquakes with centroid depths of ≥6 km are 0.92 and 2.91 MPa, respectively, approximately fourfold the values for earthquakes with centroid depths <6 km. Considering the significant impact to near-fault strong ground motion, the cause of this sharp transition deserves further investigation.

Evidence for a Sharp CO Snow Line Transition in a Protoplanetary Disk and Implications for Millimeter-wave Observations of CO Isotopologues

Observations of CO isotopologue emission from protoplanetary disks at millimeter wavelengths are a powerful tool for probing the CO snow line, an important marker for disk chemistry, and also for estimating total disk gas mass, a key quantity for planet formation. We use simple models to demonstrate that the vertical thickness of an isothermal layer around the disk midplane has important effects on the CO column density radial profile, with a thick layer producing a sharp CO snow line transition. We simulate next-generation Very Large Array (ngVLA) and Atacama Large Millimeter/submillimeter Array (ALMA) images to show that this sharp change in the CO column density can be detected in the derivative of the radial profile of emission from optically thin CO isotopologue lines. We apply this method to archival ALMA observations of the disk around the Herbig Ae star HD 163296 in the C17O and C18O J = 1–0 and J = 2–1 lines to identify a sharp CO snow line transition near ∼80 au (0.″8 at 101 pc), and show the CO column density decreases by more than a factor of 20. This finding is consistent with previous inferences from the steep rise of N2H+ emission, which marks the location where CO depletes. We also demonstrate that the disk’s thermal structure introduces significant systematic uncertainty to estimates of total disk gas mass derived from these lines. The substantial improvement in sensitivity envisioned for the ngVLA over ALMA for observations of ground-state lines of CO isotopologues has the potential to extend this approach to a much larger population of disks.

Synchronization transitions in adaptive simplicial complexes with cooperative and competitive dynamics.

Adaptive network is a powerful presentation to describe different real-world phenomena. However, current models often neglect higher-order interactions (beyond pairwise interactions) and diverse adaptation types (cooperative and competitive) commonly observed in systems such as the human brain and social networks. This work addresses this gap by incorporating these factors into a model that explores their impact on collective properties such as synchronization. Through simplified network representations, we investigate how the simultaneous presence of cooperative and competitive adaptations influences phase transitions. Our findings reveal a transition from first-order to second-order synchronization as the strength of higher-order interactions increases under competitive adaptation. We also demonstrate the possibility of synchronization even without pairwise interactions, provided there is strong enough higher-order coupling. When only competitive adaptations are present, the system exhibits second-order-like phase transitions and clustering. Conversely, with a combination of cooperative and competitive adaptations, the system undergoes a first-order-like phase transition, characterized by a sharp transition to the synchronized state without reverting to an incoherent state during backward transitions. The specific nature of these second-order-like transitions varies depending on the coupling strengths and mean degrees. With our model, we can control not only when the system synchronizes but also the way the system goes to synchronization.

Formation of the Cu+Nb Interlayer in the Inconel 718/Ti6Al4V Multi-Material Obtained by Selective Laser Melting.

This study examines the Inconel 718/Ti6Al4V multi-material with a Cu and Nb interlayer produced by SLM. To achieve this, it is necessary to investigate the microstructure, the chemical and phase composition, and the hardness of the interfacial zone in the multi-material samples. Furthermore, it is necessary to determine the impact of interlayer utilization on the mechanical properties of multi-material samples. The investigation showed that the formation of island macro-segregation was observed in all interfacial zones of the multi-material samples. The interfacial zones, Ti6Al4V/Nb and Cu/Inconel 718, exhibited a relatively sharp transition in the chemical composition. In contrast, the Cu/Nb interfacial zone exhibited a gradual transition. The results of the chemical composition study indicated that the width of the Nb/Cu transition zone was approximately 700 μm. No new phases were identified in the production of the multi-material samples. The typical phases were present in the alloy zone, as well as in the Nb/Cu interfacial zone. During the transition from the Ti6Al4V zone to the Inconel 718 zone through the Nb and Cu zones, the average microhardness values changed as follows: 270 → 190 → 120 → 300 HV. The ultimate tensile strength values for the multi-material samples reached 910 MPa.

Shifting temperature-abundance relationship for Bering Sea walleye pollock consistent with northward expansion during exceptionally warm conditions

Rapid climate change in high-latitude ecosystems presents a challenge to fisheries management, as ecosystems are exposed to novel climate conditions that might expose non-stationary climate-biology relationships. Recently, the eastern Bering Sea has experienced a series of warm years outside the range of previous observations, resulting in shifting species distributions. We tested whether exceptionally warm temperatures from 2014-2019 revealed temporal non-stationarity in the relationship between temperature and the local abundances of walleye pollock Gadus chalcogrammus, an ecologically and commercially important species. Using survey catch per unit effort (CPUE) as a local abundance proxy, we detected a gradual shift through time in the local abundance-bottom temperature relationship, but little evidence for a sharp transition associated with marine heatwave conditions. Because pollock have expanded their range into novel habitats in the northeast Bering Sea (NEBS), we tested whether our models, parameterized for the southeast Bering Sea (SEBS), had predictive skill in the northeast. Our models were generally able to identify areas of high and low CPUE, though they under-predicted the magnitude of abundance observed in the northeast during the warm years. Spatial associations between pollock and other species differed between the warm period (2014-2019) and previous decades (1982-2013) for 3 of 9 species, providing mixed evidence for non-stationarity. These findings contrast with results showing sharp rather than gradual changes in climate-biology relationships associated with climate transitions in nearby ecosystems. The same processes that govern walleye pollock abundance and distribution appear to apply to both the SEBS, historically the core of their distribution, and the NEBS.

A Polycarbonate-Assisted Transfer Method for van der Waals Contacts to Magnetic Two-Dimensional Materials.

Magnetic two-dimensional (2D) materials have garnered significant attention for their potential to revolutionize 2D spintronics due to their unique magnetic properties. However, their air-sensitivity and highly insulating nature of the magnetic semiconductors present substantial challenges for device fabrication with effective contacts. In this study, we introduce a polycarbonate (PC)-assisted transfer method that effectively forms van der Waals (vdW) contacts with 2D materials, streamlining the fabrication process without the need for additional lithography. This method is particularly advantageous for air-sensitive magnetic materials, as demonstrated in Fe3GeTe2. It also ensures excellent interface contact quality and preserves the intrinsic magnetic properties in magnetic semiconductors like CrSBr. Remarkably, this method achieves a contact resistance four orders of magnitude lower than that achieved with traditional thermally evaporated electrodes in thin-layer CrSBr devices and enables the observation of sharp magnetic transitions similar to those observed with graphene vdW contacts. Compatible with standard dry-transfer processes and scalable to large wafer sizes, our approach provides a straightforward and effective solution for developing complex magnetic heterojunction devices and expanding the applications of magnetic 2D materials.

Regularized-renormalized-resummed loop corrected power spectrum of non-singular bounce with Primordial Black Hole formation

We present a complete and consistent exposition of the regularization, renormalization, and resummation procedures in the setup of having a contraction and then non-singular bounce followed by inflation with a sharp transition from slow-roll (SR) to ultra-slow roll (USR) phase for generating primordial black holes (PBHs). We consider following an effective field theory (EFT) approach and study the quantum loop corrections to the power spectrum from each phase. We demonstrate the complete removal of quadratic UV divergences after renormalization and softened logarithmic IR divergences after resummation and illustrate the scheme-independent nature of our renormalization approach. We further show that the addition of a contracting and bouncing phase allows us to successfully generate PBHs of solar-mass order, MPBH∼O(M⊙)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_\ extrm{PBH}\\sim \\mathcal{O}(M_{\\odot })$$\\end{document}, by achieving the minimum e-folds during inflation to be ΔNTotal∼O(60)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta N_{\ extrm{Total}}\\sim \\mathcal{O}(60)$$\\end{document} and in this process successfully evading the strict no-go theorem. We notice that varying the effective sound speed between 0.88⩽cs⩽1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0.88\\leqslant c_{s}\\leqslant 1$$\\end{document}, allows the peak spectrum amplitude to lie within 10-3⩽A⩽10-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-3}\\leqslant A \\leqslant 10^{-2}$$\\end{document}, indicating that causality and unitarity remain protected in the theory. We analyse PBHs in the extremely small, MPBH∼O(10-33-10-27)M⊙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{\ extrm{PBH}}\\sim \\mathcal{O}(10^{-33}-10^{-27})M_{\\odot }$$\\end{document}, and the large, MPBH∼O(10-6-10-1)M⊙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{\ extrm{PBH}}\\sim \\mathcal{O}(10^{-6}-10^{-1})M_{\\odot }$$\\end{document}, mass limits and confront the PBH abundance results with the latest microlensing constraints. We also study the cosmological beta functions across all phases and find their interpretation consistent in the context of bouncing and inflationary scenarios while satisfying the pivot scale normalization requirement. Further, we estimate the spectral distortion effects and shed light on controlling PBH overproduction.

Charting Cortical-Layer Specific Area Boundaries Using Gibbs Ringing Attenuated T1w/T2w-FLAIR Myelin MRI.

Cortical areas have traditionally been defined by their distinctive layer cyto- and/or myelo- architecture using postmortem histology. Recent studies have delineated many areas by measuring overall cortical myelin content and its spatial gradients using the T1w/T2w ratio MRI in living primates, including humans. While T1w/T2w studies of areal transitions might benefit from using the layer profile of this myelin-related contrast, a significant confound is Gibbs ringing artefact, which produces signal fluctuations resembling cortical layers. Here, we address these issues with a novel approach using cortical layer thickness-adjusted T1w/T2w-FLAIR imaging, which effectively cancels out Gibbs ringing artefacts while enhancing intra-cortical myelin contrast. Whole-brain MRI measures were mapped onto twelve equivolumetric layers, and layer-specific sharp myeloarchitectonic transitions were identified using spatial gradients resulting in a putative 182 area/subarea partition of the macaque cerebral cortex. The myelin maps exhibit unexpectedly high homology with humans suggesting cortical myelin shares the same developmental program across the species. Comparison with histological Gallyas myelin stains explains over 80% of the variance in the laminar T1w/T2w-FLAIR profiles, substantiating the validity of the method. Altogether, our approach provides a novel, noninvasive means for precision mapping layer myeloarchitecture in the primate cerebral cortex, advancing the pioneering work of classical neuroanatomists.

Palette‐Based Recolouring of Gradient Meshes

AbstractGradient meshes are a vector graphics primitive formed by a regular grid of bicubic quad patches. They allow for the creation of complex geometries and colour gradients, with recent extensions supporting features such as local refinement and sharp colour transitions. While many methods exist for recolouring raster images, often achieved by modifying an automatically detected palette of the image, gradient meshes have not received the same amount of attention when it comes to global colour editing. We present a novel method that allows for real‐time palette‐based recolouring of gradient meshes, including gradient meshes constructed using local refinement and containing sharp colour transitions. We demonstrate the utility of our method on synthetic illustrative examples as well as on complex gradient meshes.

Coarse-Grain Model of Ultrarigid Polymer Rods Comprising Bifunctionally Linked Peptide Bundlemers.

Computationally designed homotetrameric helical peptide bundles have been functionalized at their N-termini to achieve supramolecular polymers, wherein individual bundles ("bundlemers") are the monomeric units. Adjacent bundles are linked via two covalent cross-links. The polymers exhibit a range of conformational properties, including formation of rigid-rods with micrometer-scale persistence lengths. Herein, a coarse-grained model is used to illuminate how molecular features affect the rod-like behavior of the polymers. With increasing affinity between bundlemer ends, a sharp transition in the persistence length is observed. Doubly linked chains exhibit larger persistence lengths and more robust formation of rigid-rod structures than singly linked chains. Chain stiffness increases with decreasing temperatures. Increasing the length of the cross-linker results in more flexible chains. This model provides insights into how molecular features control the structural properties of chains comprising doubly linked rigid bundlemers.

Propaganda and thought work in the Mao era: Absoluteness, sharp transitions, and political instability

AbstractThis paper elucidates the reasons behind Deng Xiaoping's initiation of political reform from a propaganda perspective by examining the features of Mao's propaganda and thought work and their implications for the Chinese Communist Party, analyzing cases such as the “Two‐Hundred Policy,” the “Anti‐Rightist Campaign,” propaganda campaigns related to the USSR, and the transformation of Lin Biao's image. It argues that Mao's propaganda and thought work, characterized by their absoluteness and sharp transitions, were detrimental to the stability of the communist regime. These characteristics led to widespread indifference, distrust, and even resistance toward the Chinese Communist Party among the Chinese populace since the late Mao era. China had entered a post‐trust era, marked by a growing tendency among the populace to preemptively view official messages as untrustworthy. To restore the party's credibility, Deng Xiaoping initiated reforms in propaganda and thought work to address these shortcomings.

A high-frequency, low-power resonant radio-frequency neutron spin flipper for high-resolution spectroscopy.

We present a resonant-mode, transverse-field, radio-frequency (rf) neutron spin flipper design that uses high-temperature superconducting films to ensure sharp transitions between uniform magnetic field regions. Resonant mode allows for low-power, high-frequency operation but requires strict homogeneity of the magnetic fields inside the device. This design was found to efficiently flip neutrons at 96.6 ± 0.6% at an effective frequency of 4MHz in bootstrap configuration with a beam size of 2.4 × 2.5 cm2 and a wavelength of 0.4nm. The high frequency and efficiency enable this device to perform high-resolution neutron spectroscopy with comparable performance with currently implemented rf flipper designs. The limitation of the maximum frequency was found due to the field homogeneity of the device. We numerically analyze the maximum possible efficiency of this design using a Bloch solver simulation with magnetic fields generated from finite-element simulations. We also discuss future improvements of the efficiency and frequency to the design based on the experimental and simulation results.

Smooth Attention: Improving Image Semantic Segmentation

Attention mechanisms have become a fundamental component of deep learning, including the field of computer vision. The key idea behind attention in computer vision is to help the model focus on the relevant spatial regions of the input image, rather than treating all regions equally. The traditional approaches to attention mechanisms in computer vision often suffer from distribution inconsistencies in the attention maps, resulting in sharp transitions that negatively affect model’s focus and lead to poor generalization on complex shapes. The problem of spatial incoherence is particularly pronounced in the task of semantic segmentation, where accurate pixel-level predictions require a detailed understanding of the spatial relationships within the image. In this paper, we propose an attention mechanism called Smooth Attention designed for convolutional neural networks to address the problem of spatial inconsistency in attention maps through multidime- nsional spatial smoothing. We conduct a series of experiments to evaluate the effectiveness of the proposed mechanism and demonstrate its superior performance compared to traditional methods.

Ultralow-Power Circuit and Sensing Applications Based on Subthermionic Threshold Switching Transistors.

The most recent breakthrough in state-of-the-art electronics and optoelectronics involves the adoption of steep-slope field-effect transistors (FETs), promoting sub-60 mV/dec subthreshold swing (SS) at ambient temperature, effectively overcoming "Boltzmann limit" to minimize power consumption. Here, a series integration of nanoscale copper-based resistive-filamentary threshold switch (TS) with the IGZO channel-based FET is used to develop a TS-FET, in which the turn-on characteristics exhibit an abrupt transition over five decades, with an extremely low SS of 7 mV/dec, a high on/off ratio (>109), and ultralow leakage current (40-fold decrease), ensuring excellent repeatability and device yield. Unlike previous device-centric studies, this work highlights potential circuit applications (logic-inverter, pulse-sensor amplification, and photodetector) based on TS-FET. The sharp transition behavior of TS-FET enables the establishment of logic inverters with a high voltage gain of ≈800, with a circuit-level demonstration achieving a bias-independent record-high intrinsic gain (>1000). A wearable pulse sensor integrated with an amplifier circuit ensured the precise amplification of electrophysical signals by 450 times. In addition, the application of a TS-FET-based photodetector features high responsivity (1.08 × 104 mA/W) and detectivity (1.03 × 1020 Jones). The low-power strategy of TS-FETs is promising for the development of energy-efficient integrated circuits alongside sensor-interconnected biomedical applications in wearable technology.

High Quantum Yields and Biomedical Fluorescent Imaging Applications of Photosensitized Trivalent Lanthanide Ion-Based Nanoparticles.

In recent years, significant advances in enhancing the quantum yield (QY) of trivalent lanthanide (Ln3+) ion-based nanoparticles have been achieved through photosensitization, using host matrices or capping organic ligands as photosensitizers to absorb incoming photons and transfer energy to the Ln3+ ions. The Ln3+ ion-based nanoparticles possess several excellent fluorescent properties, such as nearly constant transition energies, atomic-like sharp transitions, long emission lifetimes, large Stokes shifts, high photostability, and resistance to photobleaching; these properties make them more promising candidates as next-generation fluorescence probes in the visible region, compared with other traditional materials such as organic dyes and quantum dots. However, their QYs are generally low and thus need to be improved to facilitate and extend their applications. Considerable efforts have been made to improve the QYs of Ln3+ ion-based nanoparticles through photosensitization. These efforts include the doping of Ln3+ ions into host matrices or capping the nanoparticles with organic ligands. Among the Ln3+ ion-based nanoparticles investigated in previous studies, this review focuses on those containing Eu3+, Tb3+, and Dy3+ ions with red, green, and yellow emission colors, respectively. The emission intensities of Eu3+ and Tb3+ ions are stronger than those of other Ln3+ ions; therefore, the majority of the reported studies focused on Eu3+ and Tb3+ ion-based nanoparticles. This review discusses the principles of photosensitization, several examples of photosensitized Ln3+ ion-based nanoparticles, and in vitro and in vivo biomedical fluorescent imaging (FI) applications. This information provides valuable insight into the development of Ln3+ ion-based nanoparticles with high QYs through photosensitization, with future potential applications in biomedical FI.

Exploring anti-ferroelectric thin films with high energy storage performance by moderating phase transition

Anti-ferroelectric thin films are renowned for their signature double hysteresis loops and sheds light on the distinguished energy storage capabilities of dielectric capacitors in modern electronic devices. However, anti-ferroelectric capacitors are still facing the dual challenges of low energy density and efficiency to achieve state-of-the-art performance. Their large hysteresis and sharp first-order phase transition usually results in a low energy storage efficiency and easy breakdown, severely obscuring its future application. In this study, we demonstrate that anti-ferroelectric (Pb0.97La0.02)(Zr1−xSnx)O3 epitaxial thin films exhibit enhanced energy storage performance through local structural heterogeneity to moderate the first-order phase transition by calculating the corresponding polarization as a function of switching time for the first time. The films exhibit remarkable enhanced breakdown strength (∼3.47 MV/cm, ∼5 times the value for PbZrO3) and energy storage performance. Our endeavors have culminated in the ingenious formulation of a novel strategy, namely, the postponement of polarization processes, thereby elevating the breakdown strength and total energy storage performance. This landmark achievement has unveiled a fresh vista of investigative opportunities for advancing the energy storage prowess of electric dielectrics.

On the ground state of one-dimensional quantum droplets for large chemical potentials

Abstract In the present work we revisit the problem of the quantum droplet in atomic Bose–Einstein condensates with an eye towards describing its ground state in the large density, so-called Thomas–Fermi (TF) limit. We consider the problem as being separable into 3 distinct regions: an inner one, where the TF approximation is valid, a sharp transition region where the density abruptly drops towards the (vanishing) background value and an outer region which asymptotes to the background value. We analyze the spatial extent of each of these regions, and develop a systematic effective description of the rapid intermediate transition region. Accordingly, we derive a uniformly valid description of the ground state that is found to accurately match our numerical computations. As an additional application of our considerations, we show that this formulation allows for an analytical approximation of excited states such as the (trapped) dark soliton in the large density limit.

A pyroxene-based quantum magnet with multiple magnetization plateaus.

Pyroxenes (AMX2O6) consisting of infinite one-dimensional edge-sharing MO6 chains and bridging XO4 tetrahedra are fertile ground for finding quantum materials. Thus, here, we have studied calcium cobalt germanate (CaCoGe2O6) and calcium cobalt silicate (CaCoSi2O6) crystals in depth. Heat capacity data show that the spins in both compounds are dominantly Ising-like, even after being manipulated by high magnetic fields. On cooling below the Néel temperatures, a sharp field-induced transition in magnetization is observed for CaCoGe2O6, while multiple magnetization plateaus beneath the full saturation moment are spotted for CaCoSi2O6. Our analysis shows that these contrasting behaviors potentially arise from the different electron configurations of germanium and silicon, in which the 3d orbitals are filled in the former but empty in the latter, enabling electron hopping. Thus, silicate tetrahedra can aid the interchain superexchange pathway between cobalt(II) ion centers, while germanate ones tend to block it during magnetization.