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The search for new functional materials with tunable properties remains a central challenge in chemistry, particularly for applications in energy and electronics. In this work, we present a framework for predictive crystal design in alkali metal chalcogenides that enables controlled dimensional reduction of a parent covalent motif, yielding a broad range of electronic structures, which systematically evolve from one parent to the other. We present 11 new members of the AnCu4–nSnS4 family (A = alkali metal; n = 0–4), which reduce the three-dimensional (3D) covalent network of Cu4SnS4 into various 3D, 2D, 1D, and 0D [Cu4–nSnS4]n− motifs through the substitution of Cu with alkali metals of various radii. The end members of the family set the range in achievable band gaps at 0.99 eV for fully covalent Cu4SnS4 (n = 0) and 3.38 eV for K4SnS4 (n = 4) with 0D [SnS4]n− tetrahedra. As the dimensionality of [Cu4–nSnS4]n− systematically reduces within AnCu4–nSnS4 (n = 1–3), a stepwise increase in band gap energy occurs through a gradual decrease in the energy of the valence band maximum and an increase in the conduction band minimum, with an increase in the effective masses of charge carriers. Furthermore, irrespective of the alkali metal, the thermal stability decreases with decreasing [Cu4–nSnS4]n− dimensionality within the quaternary members. Most importantly, we demonstrate that predictable crystal structure and property evolution for a given composition space is possible by deriving a general formula based on substituting the covalent metals of a parent structure with alkali metals. 

Abstract We analyze the dense gas kinematics in two class 0/I protostellar cores, Per 30 and NGC 1333 IRAS 7, in the Perseus Molecular Cloud to determine whether their velocity structures are indicative of rotation. We examine the hyperfine structure of the N₂H⁺J= 1–0 transition by combining 3″ (900 au) Atacama Large Millimeter/submillimeter Array measurements with 9″ (2700 au) measurements from the Green Bank Telescope. We use theCASA Feathermethod to combine these data in order to maximize our sensitivity across spatial scales. We fit the N₂H⁺spectra to constrain the centroid velocity of the gas at each pixel and use these values to calculate the linear velocity gradient and specific angular momentum within apertures centered on each protostar with radii ranging from 5″ to 60″. Our results indicate that the velocity structure probed by the N₂H⁺emission is likely not a result of core rotation. These findings are consistent with other studies in the literature that indicate rotation is often not evident on scales ≲1000 au. We instead suggest that the velocity structure we see is a result of torques caused by irregular density distributions in these protostellar systems. 

Abstract Star formation is a fundamental, yet poorly understood, process of the Universe. It is important to study how star formation occurs in different galactic environments. Thus, here, in the first of a series of papers, we introduce the Low-metallicity Star Formation (LZ-STAR) survey of the Sh2-284 (hereafter S284) region, which, atZ ∼  0.3–0.5Z_⊙, is one of the lowest-metallicity star-forming regions of our Galaxy. LZ-STAR is a multifacility survey, including observations with JWST, the Atacama Large Millimeter/submillimeter Array (ALMA), Hubble Space Telescope, Chandra, and Gemini. As a starting point, we report JWST and ALMA observations of one of the most massive protostars in the region, S284p1. The observations of shock-excited molecular hydrogen reveal a symmetric, bipolar outflow originating from the protostar, spanning several parsecs, and fully covered by the JWST field of view and ALMA observations of CO(2–1) emission. These allow us to infer that the protostar has maintained a relatively stable orientation of disk accretion over its formation history. The JWST near-infrared continuum observations detect a centrally illuminated bipolar outflow cavity around the protostar, as well as a surrounding cluster of low-mass young stars. We develop new radiative transfer models of massive protostars designed for the low metallicity of S284. Fitting these models to the protostar’s spectral energy distribution implies a current protostellar mass of ∼10M_⊙has formed from an initial ∼100M_⊙core over the last ∼3 × 10⁵yr. Overall, these results indicate that massive stars can form in an ordered manner in low-metallicity, protocluster environments. 

Abstract The vertical settling of dust grains in a circumstellar disk, characterized by their scale height, is a pivotal process in the formation of planets. This study offers in-depth analysis and modeling of the radial scale height profile of dust grains in the HL Tau system, leveraging high-resolution polarization observations. We resolve the inner disk’s polarization, revealing a significant nearside–farside asymmetry, with the nearside being markedly brighter than the farside in polarized intensity. This asymmetry is attributed to a geometrically thick inner dust disk, suggesting a large aspect ratio ofH/R≥ 0.15, whereHis the dust scale height andRis the radius. The first ring at 20 au exhibits an azimuthal contrast, with polarization enhanced along the minor axis, indicating a moderately thick dust ring withH/R ≈ 0.1. The absence of the nearside–farside asymmetry at larger scales implies a thin dust layer, withH/R < 0.05. Taken together, these findings depict a disk with a turbulent inner region and a settled outer disk, requiring a variable turbulence model withαincreasing from 10⁻⁵at 100 au to 10^−2.5at 20 au. This research sheds light on dust settling and turbulence levels within protoplanetary disks, providing valuable insights into the mechanisms of planet formation. 

Abstract Polarization observations of the Milky Way and many other spiral galaxies have found a close correspondence between the orientation of spiral arms and magnetic field lines on scales of hundreds of parsecs. This paper presents polarization measurements at 214μm toward 10 filamentary candidate “bones” in the Milky Way using the High-resolution Airborne Wide-band Camera on the Stratospheric Observatory for Infrared Astronomy. These data were taken as part of the Filaments Extremely Long and Dark: A Magnetic Polarization Survey and represent the first study to resolve the magnetic field in spiral arms at parsec scales. We describe the complex yet well-defined polarization structure of all 10 candidate bones, and we find a mean difference and standard deviation of −74° ± 32° between their filament axis and the plane-of-sky magnetic field, closer to a field perpendicular to their length rather than parallel. By contrast, the 850μm polarization data from Planck on scales greater than 10 pc show a nearly parallel mean difference of 3° ± 21°. These findings provide further evidence that magnetic fields can change orientation at the scale of dense molecular clouds, even along spiral arms. Finally, we use a power law to fit the dust polarization fraction as a function of total intensity on a cloud-by-cloud basis and find indices between −0.6 and −0.9, with a mean and standard deviation of −0.7 ± 0.1. The polarization, dust temperature, and column density data presented in this work are publicly available online. 

ABSTRACT We investigate the dynamics of dust concentration in actively accreting, substructured, non-ideal magnetohydrodynamic wind-launching discs using two-dimensional and three-dimensional (3D) simulations incorporating pressureless dust fluids of various grain sizes and their aerodynamic feedback on gas dynamics. Our results reveal that mm/cm-sized grains are preferentially concentrated within the inner 5–10 au of the disc, where the dust-to-gas surface density ratio (local metallicity Z) significantly exceeds the canonical 0.01, reaching values up to 0.25. This enhancement arises from the interplay of dust settling and complex gas flows in the meridional plane, including mid-plane accretion streams at early times, mid-plane expansion driven by magnetically braked surface accretion at later times, and vigorous meridional circulation in spontaneously formed gas rings. The resulting size-dependent dust distribution has a strong spatial variation, with large grains preferentially accumulating in dense rings, particularly in the inner disc, while being depleted in low-density gas gaps. In 3D, these rings and gaps are unstable to Rossby wave instability, generating arc-shaped vortices that stand out more prominently than their gas counterparts in the inner disc because of preferential dust concentration at small radii. The substantial local enhancement of the dust relative to the gas could promote planetesimal formation via streaming instability, potentially aided by the ‘azimuthal drift’ streaming instability that operates efficiently in accreting discs and a lower Toomre Q expected in younger discs. Our findings suggest that actively accreting young discs may provide favourable conditions for early planetesimal formation, which warrants further investigation. 

Quantum state purification is the task of recovering a nearly pure copy of an unknown pure quantum state using multiple noisy copies of the state. This basic task has applications to quantum communication over noisy channels and quantum computation with imperfect devices, but has only been studied previously for the case of qubits. We derive an efficient purification procedure based on the swap test for qudits of any dimension, starting with any initial error parameter. Treating the initial error parameter and the dimension as constants, we show that our procedure has sample complexity asymptotically optimal in the final error parameter. Our protocol has a simple recursive structure that can be applied when the states are provided one at a time in a streaming fashion, requiring only a small quantum memory to implement. 

ABSTRACT Recent high angular resolution ALMA observations have revealed rich information about protoplanetary discs, including ubiquitous substructures and three-dimensional gas kinematics at different emission layers. One interpretation of these observations is embedded planets. Previous 3D planet–disc interaction studies are either based on viscous simulations or non-ideal magnetohydrodynamics (MHD) simulations with simple prescribed magnetic diffusivities. This study investigates the dynamics of gap formation in 3D non-ideal MHD discs using non-ideal MHD coefficients from the look-up table that is self-consistently calculated based on the thermochemical code. We find a concentration of the poloidal magnetic flux in the planet-opened gap (in agreement with previous work) and enhanced field-matter coupling due to gas depletion, which together enable efficient magnetic braking of the gap material, driving a fast accretion layer significantly displaced from the disc mid-plane. The fast accretion helps deplete the gap further and is expected to negatively impact the planet growth. It also affects the corotation torque by shrinking the region of horseshoe orbits on the trailing side of the planet. Together with the magnetically driven disc wind, the fast accretion layer generates a large, persistent meridional vortex in the gap, which breaks the mirror symmetry of gas kinematics between the top and bottom disc surfaces. Finally, by studying the kinematics at the emission surfaces, we discuss the implications of planets in realistic non-ideal MHD discs on kinematics observations.