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Some cerium and uranium compounds exhibit unusual transport properties due to localized electron states. Recent experiments demonstrate that quantum interference on frustrated lattices provides an alternative route to this behaviour.

Nematicity, spontaneous breaking of rotational symmetry, is a ubiquitous phenomenon in correlated quantum matter. Here we show a phase transition in high-quality ScV 6 Sn 6 bilayer kagome metal at a temperature T * , occurring seven Kelvins below the charge density wave transition at T C D W , as indicated by thermodynamic, transport, and optical measurements. This emerging intermediate phase does not exhibit spontaneous time-reversal-symmetry breaking, as evidenced by zero-field Sagnac interferometry. However, it displays a strong, spontaneous in-plane anisotropy between T * and T C D W , revealed by transport and optical polarization rotation measurements. A pronounced depolarization effect detected by the Sagnac interferometer further confirms its nematic nature. Unlike AV 3 Sb 5 , this phase, alongside the recently discovered intra-unit cell nematic order at lower temperatures, presents a diverse landscape of nematicities at multiple length and temperature scales. Our findings highlight ScV 6 Sn 6 as a prime candidate for realizing symmetry-breaking phases driven by charge density competition, kagome physics, and Van Hove singularities. Nematicity, the spontaneous breaking of lattice rotational symmetry, plays an important role in kagome metals. Here, the authors report on a nematic phase within seven Kelvin below the charge density wave transition in the bilayer kagome metal ScV 6 Sn 6 .

Kagomé metals are widely recognized, versatile platforms for exploring topological properties, unconventional electronic correlations, magnetic frustration, and superconductivity. In the RV6Sn6 family of materials (R = Sc, Y, Lu), ScV6Sn6 hosts an unusual charge density wave ground state as well as structural similarities with the AV3Sb5 system (A = K, Cs, Rb). In this work, we combine Raman scattering spectroscopy with first-principles lattice dynamics calculations to reveal phonon mixing processes in the charge density wave state of ScV6Sn6. In the low temperature phase, we find at least four new peaks in the vicinity of the V-containing totally symmetric mode near 240 cm−1 suggesting that the density wave acts to mix modes of P6/mmm and R3¯m symmetry - a result that we quantify by projecting phonons of the high symmetry state onto those of the lower symmetry structure. We also test the stability of the short-range ordered density wave state under compression and propose that both physical and chemical pressure quench the effect. We discuss these findings in terms of symmetry and the structure-property trends that can be unraveled in this system.

Magnetism is widely considered to be a key ingredient of unconventional superconductivity. In contrast to cuprate high-temperature superconductors, antiferromagnetism in most Fe-based superconductors (FeSCs) is characterized by a pair of magnetic propagation vectors, ( π ,0) and (0, π ). Consequently, three different types of magnetic order are possible. Of these, only stripe-type spin-density wave (SSDW) and spin-charge-density wave (SCDW) orders have been observed. A realization of the proposed spin-vortex crystal (SVC) order is noticeably absent. We report a magnetic phase consistent with the hedgehog variation of SVC order in Ni-doped and Co-doped CaKFe 4 As 4 based on thermodynamic, transport, structural and local magnetic probes combined with symmetry analysis. The exotic SVC phase is stabilized by the reduced symmetry of the CaKFe 4 As 4 structure. Our results suggest that the possible magnetic ground states in FeSCs have very similar energies, providing an enlarged configuration space for magnetic fluctuations to promote high-temperature superconductivity. Iron-based superconductors: making a hedgehog spin-vortex crystal The magnetic texture of a new superconductor adopts a in-out spin, spin-vortex crystal motif, fulfilling theoretical predictions. Many iron-based superconductors have magnetic phases arising from combining two basic magnetic structures, but only two of three possible combinations had previously been observed. A team led by Paul Canfield of Iowa State University and Ames Laboratory have synthesised a material with the third type of magnetic structure called a hedgehog spin-vortex crystal. The authors began with a compound with spatial symmetry that could help stabilise the structure, but without magnetic order. By tuning the chemical composition they induced magnetism and successfully obtained the desired phase. The sensitivity of the magnetic state to the symmetry and composition indicates that different phases are energetically close, suggesting magnetic fluctuations may play a significant role in the physics of iron-based superconductors.

Kagome lattices host flat bands due to their frustrated lattice geometry, which leads to destructive quantum interference of electron wave functions. Here, we report imaging of the kagome flat band localization in real-space using scanning tunneling microscopy. We identify both the Fe 3 Sn kagome lattice layer and the Sn 2 honeycomb layer with atomic resolution in kagome antiferromagnet FeSn. On the Fe 3 Sn lattice, at the flat band energy determined by the angle resolved photoemission spectroscopy, tunneling spectroscopy detects an unusual state localized uniquely at the Fe kagome lattice network. We further show that the vectorial in-plane magnetic field manipulates the spatial anisotropy of the localization state within each kagome unit cell. Our results are consistent with the real-space flat band localization in the magnetic kagome lattice. We further discuss the magnetic tuning of flat band localization under the spin–orbit coupled magnetic kagome lattice model. Direct imaging and tuning of flat band localization in kagome materials remains a challenge. Here, scanning tunneling microscopy and photoemission spectroscopy are used to study FeSn, revealing real-space localization and magnetic tuning of the flat band state within the Fe 3 Sn kagome lattice layer.

Assessing the cytoplasmic uptake of fluorescently-tagged drugs in heterogeneous cell types currently involves time-consuming manual segmentation of confocal microscopy images. We developed a set of methods that incorporate map algebra techniques to facilitate and expedite image segmentation, particularly of the parenchyma of intermediate cells in the stria vascularis of the inner ear. Map algebra is used to apply a convolution kernel to pixel neighborhoods to create a masking image to select pixels in the original image for further operations. Here, we describe the utility of integrated intensity-based, percentile-based, and local autocorrelation-based methods to automate segmentation of images into putative morphological regions for pixel intensity analysis. Integrated intensity-based methods are variants of watershed segmentation tools that determine morphological boundaries from rates of change in integrated pixel intensity. Percentile- and local autocorrelation-based methods evolved out of the process of developing map algebra- and integrated intensity-based tools. We identified several simplifications that are surprisingly effective for image segmentation and pixel intensity analysis. These methods were empirically validated on three levels: first, the algorithms were developed based on iterations of inspected results; second, algorithms were tested for various types of robustness; and third, developed algorithms were validated against results from manually-segmented images. We conclude the key to automated segmentation is supervision of output data.

The compound Ag 3 Sn adopts the ordered orthorhombic D0 a Cu 3 Ti-type structure. It exhibits an unusual low yield stress and high ductility for an intermetallic compound, but the reasons for these effects are not clear. Here, we report an electron microscopy study on the defects present in solution-grown Ag 3 Sn single crystals that have deformed during the decanting and subsequent handling processes. It is found that the crystals contain two types of lenticular deformation twins: {011}-type and {211}-type. These twins interpenetrate with no evidence of cracking at the intersections. The crystals also contain high densities of dislocations including long straight dipoles with b   =  ± [010] and shorter curved segments and loops with b   =  [ 10 2 ¯ ] and [001]. It is inferred that the dipoles are artifacts of specimen preparation that climb in from the cross-sectional sample surfaces, whereas the shorter segments are deformation debris. If a combination of twinning and dislocation glide of the types observed here were to form concurrently during general deformation of Ag 3 Sn, then they could provide the necessary number of independent deformation modes to accommodate an arbitrary plastic strain, which might help to explain the unusual ductility of this compound.

Alloying in metal castings is one of the principal methods of strengthening an alloy for various structural and functional applications, but very rarely does it modify an alloy’s elastic modulus. We report a methodology of combining isostructural Laves phases to form a multi-component, high symmetry, isotropic phase that was discovered to enhance the elastic modulus of a cast aluminum alloy to 91.5 ± 7.4 GPa. Flux grown single crystals of the rhombicuboctahedron phase (RCO), so named for the observed morphology, were used to enhance understanding of the structure and mechanical properties of the phase. The pure RCO phase’s structure and site occupancies were co-refined using x-ray and neutron diffraction. Dynamic nanomechanical testing of the cast alloy shows the primary RCO phase has a high, relatively isotropic, elastic modulus. This RCO containing aluminum alloy is found to have a specific modulus that exceeds that of the leading Al, Mg, Steel, and Ti alloys.The elastic properties of alloys are typically insensitive to changes in microstructure. Here, an as-cast Al-Ce alloy achieves a large Young’s modulus of approximately 92 GPa, due to the presence of isotropic, high symmetry secondary phase.

The term gastrointestinal neuromuscular disease describes a clinically heterogeneous group of disorders of children and adults in which symptoms are presumed or proven to arise as a result of neuromuscular, including interstitial cell of Cajal, dysfunction. Such disorders commonly have impaired motor activity, i.e. slowed or obstructed transit with radiological evidence of transient or persistent visceral dilatation. Whilst sensorimotor abnormalities have been demonstrated by a variety of methods in these conditions, standards for histopathological reporting remain relatively neglected. Significant differences in methodologies and expertise continue to confound the reliable delineation of normality and specificity of particular pathological changes for disease. Such issues require urgent clarification to standardize acquisition and handling of tissue specimens, interpretation of findings and make informed decisions on risk-benefit of full-thickness tissue biopsy of bowel or other diagnostic procedures. Such information will also allow increased certainty of diagnosis, facilitating factual discussion between patients and caregivers, as well as giving prognostic and therapeutic information. The following report, produced by an international working group, using established consensus methodology, presents proposed guidelines on histological techniques and reporting for adult and paediatric gastrointestinal neuromuscular pathology. The report addresses the main areas of histopathological practice as confronted by the pathologist, including suction rectal biopsy and full-thickness tissue obtained with diagnostic or therapeutic intent. For each, indications, safe acquisition of tissue, histological techniques, reporting and referral recommendations are presented.