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DOE OSTI2021

Magnetization Process of Atacamite: A Case of Weakly Coupled S = 1/2 Sawtooth Chains

We present a combined experimental and theoretical study of the mineral atacamite Cu 2 Cl(OH) 3 . Density-functional theory yields a Hamiltonian describing anisotropic sawtooth chains with weak 3D connections. Experimentally, we fully characterize the antiferromagnetically ordered state. Here, magnetic order shows a complex evolution with the magnetic field, while, starting at 31.5 T, we observe a plateaulike magnetization at about M sat /2. Based on complementary theoretical approaches, we show that the latter is unrelated to the known magnetization plateau of a sawtooth chain. Instead, we provide evidence that the magnetization process in atacamite is a field-driven canting of a 3D network of weakly coupled sawtooth chains that form giant moments.

1-dimensional spin chains↗

DOE OSTI2022

Precision Determination of the Neutral Weak Form Factor of Ca 48

In this work, we report a precise measurement of the parity-violating asymmetry $A_{\rm PV}$ in the elastic scattering of longitudinally polarized electrons from $^{48}{\rm Ca}$. We measure $A_{\rm PV} =2668\pm 106\ {\rm (stat)}\pm 40\ {\rm (syst)}$ parts per billion, leading to an extraction of the neutral weak form factor $F_{\rm W} (q=0.8733$ fm$^{-1}) = 0.1304 \pm 0.0052 \ {\rm (stat)}\pm 0.0020\ {\rm (syst)}$ and the charge minus the weak form factor $F_{\rm ch} - F_{\rm W} = 0.0277\pm 0.0055$. The resulting neutron skin thickness $R_n-R_p=0.121 \pm 0.026\ {\rm (exp)} \pm 0.024\ {\rm (model)}$~fm is relatively thin yet consistent with many model calculations. The combined CREX and PREX results will have implications for future energy density functional calculations and on the density dependence of the symmetry energy of nuclear matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Experimental Determination of 𝛼 Widths of 21 Ne Levels in the Region of Astrophysical Interest: New 17 O +𝛼 Reaction Rates and Impact on the Weak 𝑠 Process

The efficiency of the weak 𝑠 process in low-metallicity rotating massive stars depends strongly on the rates of the competing 17 O ⁡(𝛼,𝑛)⁢ 20 Ne and 17 O ⁡(𝛼,𝛾)⁢ 21 Ne reactions that determine the potency of the 16 O neutron poison. Their reaction rates are poorly known in the astrophysical energy range of interest for core helium burning in massive stars because of the lack of spectroscopic information (partial widths, spin parities) for the relevant states in the compound nucleus 21 Ne . In this Letter, we report on the first experimental determination of the 𝛼-particle spectroscopic factors and partial widths of these states using the 17 O ⁡( 7 Li, 𝑡)⁢ 21 Ne 𝛼-transfer reaction. With these the 17 O ⁡(𝛼, 𝑛)⁢ 20 Ne and 17 O ⁡(𝛼, 𝛾)⁢ 21 Ne reaction rates were evaluated with uncertainties reduced by a factor more than 3 with respect to previous evaluations and the present 17 O ⁡(𝛼, 𝑛)⁢ 20 Ne reaction rate is more than 20 times larger. Finally, the present (𝛼, 𝑛)/(𝛼, 𝛾) rate ratio favors neutron recycling and suggests an enhancement of the weak 𝑠 process in the Zr-Nd region by more than 1.5 dex in metal-poor rotating massive stars.

direct reactions↗

DOE OSTI2024

Observing magnetoanisotropic weak antilocalization in near-surface quantum wells

We investigate the effects of an in-plane magnetic field on the weak antilocalization signature of near-surface quantum wells lacking bulk and inversion symmetry. The measured magnetoconductivity, which is conductivity as a function of the out-of-plane magnetic field, exhibits a strong anisotropy with respect to the direction of the in-plane magnetic field. The twofold symmetry of the observed magnetoanisotropy originates from the competition between Rashba and Dresselhaus spin-orbit couplings. The high sensitivity of the weak antilocalization to the spin texture produced by the combined Zeeman and spin-orbit fields results in very large anisotropy ratios, reaching 100%. Using a semiclassical universal model in quantitative agreement with the experimental data, we uniquely determine the values of the Dresselhaus and Rashba parameters as well as the effective in-plane g-factor of the electrons. Understanding these parameters provides prospects for different applications ranging from spintronics to topological quantum computing. Published by the American Physical Society 2024

Farzaneh, S. M. (ORCID:0000000341450991)↗

DOE OSTI2025

Floquet-engineered fast SNAP gates in weakly coupled circuit-QED systems

Superconducting cavities with high quality factors, coupled to a fixed-frequency transmon, provide a state-of-the-art platform for quantum information storage and manipulation. The commonly used selective number-dependent arbitrary phase ( SNAP ) gate faces significant challenges in ultrahigh-coherence cavities, where the weak dispersive shifts necessary for preserving high coherence typically result in prolonged gate times. Here, in this work, we propose a protocol to achieve high-fidelity SNAP gates that are orders of magnitude faster than the standard implementation, surpassing the speed limit set by the bare dispersive shift. We achieve this enhancement by dynamically amplifying the dispersive coupling via sideband interactions, followed by quantum optimal control on the Floquet-engineered system. We also present a unified perturbation theory that explains both the gate acceleration and the associated benign drive-induced decoherence, corroborated by Floquet-Markov simulations. These results pave the way for the experimental realization of high-fidelity, selective control of weakly coupled, high-coherence cavities, and expanding the scope of optimal control techniques to a broader class of Floquet quantum systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2026

Constraints on the normal branch of DGP gravity from SPT galaxy clusters with DES and HST weak-lensing mass calibration and from P l a n c k PR4 CMB anisotropies

We present constraints on the normal branch of the Dvali-Gabadadze-Porrati (nDGP) braneworld gravity model from the abundance of massive galaxy clusters. On scales below the nDGP crossover scale r c , the nDGP model features an effective gravitylike fifth force that alters the growth of structure, leading to an enhancement of the halo mass function (HMF) on cluster scales. The enhanced cluster abundance allows for constraints on the nDGP model using cluster samples. We employ the South Pole Telescope (SPT) cluster sample, selected through the thermal Sunyaev-Zel’dovich effect with the SPT and with mass calibration using weak-lensing data from the Dark Energy Survey (DES) and the Hubble Space Telescope (HST). The cluster sample contains 1,005 clusters with redshifts 0.25 < z < 1.78 , which are confirmed with the multicomponent matched filter algorithm using optical and near-infrared data. Weak-lensing data from DES and HST enable a robust mass measurement of the cluster sample. We use DES Year 3 data for 688 clusters with redshifts z < 0.95 , and HST data for 39 clusters with redshifts 0.6 < z < 1.7 . We account for the enhancement in the HMF through a semi-analytic correction factor to the standard cosmology HMF derived from the spherical collapse model in the nDGP model. We then further calibrate this model using N -body simulations. In addition, for the first time, we analyze the primary CMB temperature and polarization anisotropy measurements from Planck PR4 within the nDGP model. We obtain a competitive constraint from the joint analysis of the SPT cluster abundance with the Planck PR4 data, and report an upper bound of 1 / H 0 r c < 1.41 at 95% when assuming a cosmology with massive neutrinos.

Vogt, S. M.L. [Munich U. Observ.; LMU Munich (main↗

DOE OSTI2025

Transition from weak to strong coupling in thermal gauge theories: Lessons from 𝒩 = 4 SYM theory

We investigate the transition between weak and strong coupling in thermal 𝒩 =4 supersymmetric Yang-Mills theory as a function of ’t Hooft coupling 𝜆 for several quantities of phenomenological interest for which next-to-leading order calculations are available in both regimes. We use Padé approximants to interpolate between the weak and strong coupling expansions and determine the location and width of the transition between the asymptotic regimes.

Gauge Theories↗

DOE OSTI2020

Enabling Seamless Integration of EV Charging Infrastructure with Weak Electric Grids

Widespread adoption of Electric Vehicles (EVs) for light, medium, and heavy-duty applications has gained significant interest. Based on ownership and user preferences, light duty and local delivery medium-duty EVs are typically connected to grid distribution networks whereas larger medium duty and heavy-duty EVs are typically connected to distribution or even sub-transmission networks. Challenges with at-scale EVs and charging infrastructure supporting them include interoperability, distribution network upgrades, surge in demand charges, power quality issues, voltage stability, etc. Based on real-world data, steady-state and dynamic assessments of light-duty EV charging with a focus on DC Fast Charging (DCFC) for weak distribution grids is presented. Three main areas of contributions in this paper include - steady state and dynamic power quality measurements and assessments using real world data, transient assessments of light duty EV integration with weak distribution networks (IEEE 13 node feeder system) under grid-connected and microgrid modes, and formulation of an intelligent charging decision algorithm to enable an impact-minimal charging.

actionable intelligence↗

DOE OSTI2022

Weakly Supervised Event Classification Using Imperfect Real-world PMU Data with Scarce Labels

This paper studies event classification using imperfect real-world phasor measurement unit (PMU) data with scarce event types (labels). By investigating the real-world PMU data, it is observed that most real-world PMU data's event type is unknown, which makes it challenging to directly use such dataset to build event classifiers as existing classification techniques require high-quality training data with known event type (i.e., label). To address this challenge, a weakly supervised learning based event classification approach is developed, which can use noisy and low-quality PMU data for the training. First, data quality issues are fixed using data preprocessing techniques and then event features are constructed from the PMU data. Using these features, a series of labeling functions are learnt to generate initial estimates of the labels of large amounts of unlabeled PMU data. As the labeling functions are learnt using the same data with scarce labels, the label estimates from the labeling functions can be correlated, noisy, and bias. To enhance these initial estimates, a generative model is developed to characterize the dependencies among the estimated labels, based on which better labels are obtained for training event classifiers. Numerical experiments using the real-world dataset from the Western Interconnection of the U.S. power transmission grid show that the proposed weakly supervised event classifier trained using the dataset with only 5% labeled data can achieve 78.4% classification accuracy.

Liu, Yunchuan↗

DOE OSTI2020

Weak-field induced nonmagnetic state in a Co-based honeycomb

Layered honeycomb magnets are of interest as potential realizations of the Kitaev quantum spin liquid (KQSL), a quantum state with long-range spin entanglement and an exactly solvable Hamiltonian. Conventional magnetically ordered states are present for all currently known candidate materials, however, because non-Kitaev terms in the Hamiltonians obscure the Kitaev physics. Current experimental studies of the KQSL are focused on 4 d or 5 d transition metal–based honeycombs, in which strong spin-orbit coupling can be expected, yielding Kitaev interaction that dominates in an applied magnetic field. In contrast, for 3 d -based layered honeycomb magnets, spin-orbit coupling is weak, and thus, Kitaev physics should be substantially less accessible. Here, we report our studies on BaCo 2 (AsO 4 ) 2 , for which we find that the magnetic order associated with the non-Kitaev interactions can be fully suppressed by a relatively low magnetic field, yielding a nonmagnetic material and implying the presence of strong magnetic frustration and weak non-Kitaev interactions.

Science & Technology - Other Topics↗

DOE OSTI2024

Advances in heavy alkaline earth chemistry provide insight into complexation of weakly polarizing Ra 2+ , Ba 2+ , and Sr 2+ cations

Numerous technologies—with catalytic, therapeutic, and diagnostic applications—would benefit from improved chelation strategies for heavy alkaline earth elements: Ra 2+ , Ba 2+ , and Sr 2+ . Unfortunately, chelating these metals is challenging because of their large size and weak polarizing power. We found 18-crown-6-tetracarboxylic acid (H 4 COCO) bound Ra 2+ , Ba 2+ , and Sr 2+ to form M(H x COCO) x–2 . Upon isolating radioactive 223 Ra from its parent radionuclides ( 227 Ac and 227 Th), 223 Ra 2+ reacted with the fully deprotonated COCO 4- chelator to generate Ra(COCO) 2- (aq) (log K Ra(COCO)2- = 5.97 ± 0.01), a rare example of a molecular radium complex. Comparative analyses with Sr 2+ and Ba 2+ congeners informed on what attributes engendered success in heavy alkaline earth complexation. Chelators with high negative charge [-4 for Ra(COCO) 2- (aq) ] and many donor atoms [≥11 in Ra(COCO) 2- (aq) ] provided a framework for stable complex formation. These conditions achieved steric saturation and overcame the weak polarization powers associated with these large dicationic metals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Weak binding effects on the structure of 40 Mg

We report while the phenomenon of one- and two-neutron ground-state halo nuclei is well established, the effects of weak binding on nuclear excitation properties remain largely unexplored. Motivated by this question and by recent data in 40 Mg we investigate the coupling of weakly bound (halo) valence neutrons to a core using the known properties of 40 Mg to explore and illustrate possible particle-core coupling schemes and their impact on the low-lying excitation spectrum.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

The Impact of Topography on the Environment and Life Cycle of Weakly and Strongly Forced MCSs during RELAMPAGO

Intense deep convection and large mesoscale convective systems (MCSs) are known to occur downstream of the Andes in subtropical South America. Deep convection is often focused along the Sierras de Córdoba (SDC) in the afternoon and then rapidly grows upscale and moves to the east overnight. However, how the Andes and SDC impact the life cycle of MCSs under varying synoptic conditions is not well understood. Two sets of terrain-modification experiments using WRF are used to investigate the impact of topography in different synoptic regimes. The first set is run on the 13–14 December 2018 MCS case from RELAMPAGO, which featured a deep synoptic trough, strong lee cyclogenesis near the SDC, an enhanced low-level jet, and rapid upscale growth of an MCS. When the Andes are reduced by 50%, the lee cyclone and low-level jet that develop are weaker than with the full Andes, and the resulting MCS is weak and moves faster to the east. When the SDC are removed, few differences between the environment and resulting MCS relative to the control run are seen. A second set of experiments are run on the 25–26 January 2019 case in which a large MCS developed over the SDC and remained tied there for an extended period under weak synoptic forcing. Finally, the experiment that produces the most similar MCS to the control is when the Andes are reduced by 50% while maintaining the height of the SDC, suggesting the SDC may play a more important role in the MCS life cycle under quiescent synoptic conditions.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2023

Simultaneous measurements of forward Thomson scattering and rotational Raman scattering in a weakly ionized plasma

This paper demonstrates a simultaneous Thomson scattering and rotational Raman scattering spectroscopy in a weakly ionized plasma in air. Thomson scattering was collected in the forward scattering direction, in order to compress the relative spectra width of Thomson scattering from the plasma. Simultaneous measurements of rotational Raman scattering were obtained in the same direction, which was not affected by the collection angles. The measurements thus yielded electron temperature (T e ) and electron number density (n e ) as well as gas temperature in a weakly ionized atmospheric pressure plasma. The separation of rotational Raman scattering and Thomson scattering occurred when the scattering angle decreased to 20 degrees in the plasma, where the air temperature was found to be 150 ± 25 °C, and electron temperature of the plasma was 0.587 ± 0.087 eV, and electron number density was (1.608 ± 0.416) × 1021 m-3. The technique could be used for various plasma and combustion diagnostics in realistic engineering environments.

He, Zichen (ORCID:0000000183159882)↗

DOE OSTI2024

Tipping points emerge from weak mutualism in metacommunities

The coexistence of obligate mutualists is often precariously close to tipping points where small environmental changes can drive catastrophic shifts in species composition. For example, microbial ecosystems can collapse by the decline of a strain that provides an essential resource on which other strains cross-feed. Here, we show that tipping points, ecosystem collapse, bistability and hysteresis arise even with very weak (non-obligate) mutualism provided the population is spatially structured. Based on numeric solutions of a metacommunity model and mean-field analyses, we demonstrate that weak mutualism lowers the minimal dispersal rate necessary to avoid stochastic extinction, while species need to overcome a mean threshold density to survive in this low dispersal rate regime. Our results allow us to make numerous predictions for mutualistic metacommunities regarding tipping points, hysteresis effects, and recovery from external perturbations, and let us draw general conclusions for ecosystems even with random, not necessarily mutualistic, interactions and systems with density-dependent dispersal rather than direct mutualistic interactions.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2023

The Effect of Splashback on Weak Lensing Mass Estimates of Galaxy Clusters and Groups

The splashback radius of a dark matter halo, which corresponds to the first apocenter radius reached by infalling matter and substructures, has been detected around galaxy clusters using a multitude of observational methods, including weak lensing measurements. In this manuscript, we present how the splashback feature in the halo density profile affects galaxy cluster masses derived through weak lensing measurements if it is not accounted for. We find that the splashback radius has an increasingly large effect on group-sized halos towards $M_{200m} \sim 10^{13.5} \mathrm{M_\odot}$. Depending on the model and the radial scale used, the cluster/group masses can be biased low by more than 0.1 dex. This bias, in turn, would result in a slightly lower $\Omega_m$ value if propagated into a cluster cosmology analysis. The splashback effect with group-sized dark matter halos may become important to consider, given the increasingly stringent cosmological constraints coming from optical wide-field surveys.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2023

Weak Gravitational Lensing of Low Surface Brightness Galaxies in the Dark Energy Year 3 Catalog

We present galaxy-galaxy lensing measurements of a sample of low surface brightness galaxies (LSBGs) drawn from the Dark Energy Survey Year 3 (Y3) data. LSBGs are diffuse galaxies with a surface brightness dimmer than the ambient night sky. Given their faintness, the use of standard observational techniques proves challenging. Weak gravitational lensing probes both the baryonic and dark matter content of galaxies, rendering it a powerful technique to estimate LSBG masses. The LSBG lens sample consists of 23, 790 total extended galaxies separated into red and blue color types at $g-i\ge 0.60$ and $g-i\le 0.60$, respectively. We use the Y3 \sc{metacalibration} shape catalog as the source sample, with a number density of $5.59 \mathrm{gal}/\mathrm{arcmin}^2$. We measure the tangential shear around the lens galaxies across angular scales of $0.25-400$ arcmin and find a signal-to-noise of 6.67 for red galaxies, 2.17 for blue galaxies, and 5.30 for the total sample. We fit a model built from two NFW profiles corresponding to the LSBG dark matter subhalo and host halo to the red LSBG shear measurements with an MCMC. We estimate the host halo mass at $7.3 ^{+2.0}_{-1.6}\times 10^{12} M_\mathrm{\odot}$. We place a 95\% upper bound on the subhalo mass at $3\times 10^{11} M_\mathrm{\odot}$. We utilize the lens sample photometry to obtain an estimate of the red LSBG stellar mass distribution. We compare the ratio between the stellar mass and the subhalo mass to the parameterized, satellite-specific SHMR. This work represents the first example of an attempted constraint on the masses of LSBGs using weak gravitational lensing.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Cyber-Informed Engineering (CIE) Guidance to Defeat Systematic OT Weaknesses

This research summary outlines the University of Illinois Information Trust Institute (ITI) team's evaluation of whether applying the 12 Cyber-Informed Engineering (CIE) Principles could reduce or eliminate weaknesses identified by the SEI-ETF in engineered systems. ITI's findings suggest that applying CIE principles to weaknesses in MITRE CWE View 1358 can potentially mitigate or eliminate those vulnerabilities.

42 ENGINEERING↗