The coexistence and competition between superconductivity and electronic orders, such as spin or charge density waves, have been a central issue in high transition-temperature (Tc) superconductors. ...Unlike other iron-based superconductors, FeSe exhibits nematic ordering without magnetism whose relationship with its superconductivity remains unclear. Moreover, a pressure-induced fourfold increase of Tc has been reported, which poses a profound mystery. Here we report high-pressure magnetotransport measurements in FeSe up to ∼15 GPa, which uncover the dome shape of magnetic phase superseding the nematic order. Above ∼6 GPa the sudden enhancement of superconductivity (Tc≤38.3 K) accompanies a suppression of magnetic order, demonstrating their competing nature with very similar energy scales. Above the magnetic dome, we find anomalous transport properties suggesting a possible pseudogap formation, whereas linear-in-temperature resistivity is observed in the normal states of the high-Tc phase above 6 GPa. The obtained phase diagram highlights unique features of FeSe among iron-based superconductors, but bears some resemblance to that of high-Tc cuprates.
Strong interactions among electrons in some materials can cause them to assume configurations that are less symmetric than the underlying crystal lattice. These so-called electronic nematic states ...usually have inversion symmetry, but theorists have predicted that in metals with strong spin-orbit coupling, the inversion symmetry can be lost. Harter et al. teased out the symmetry of the electronic order in the compound Cd2Re2O7 (see the Perspective by Dodge). They found that a known structural transition in this material is a consequence of another, previously hidden electronic order that breaks inversion symmetry. Science, this issue p. 295; see also p. 246 Strong electron interactions can drive metallic systems toward a variety of well-known symmetry-broken phases, but the instabilities of correlated metals with strong spin-orbit coupling have only recently begun to be explored. We uncovered a multipolar nematic phase of matter in the metallic pyrochlore Cd2Re2O7 using spatially resolved second-harmonic optical anisotropy measurements. Like previously discovered electronic nematic phases, this multipolar phase spontaneously breaks rotational symmetry while preserving translational invariance. However, it has the distinguishing property of being odd under spatial inversion, which is allowed only in the presence of spin-orbit coupling. By examining the critical behavior of the multipolar nematic order parameter, we show that it drives the thermal phase transition near 200 kelvin in Cd2Re2O7 and induces a parity-breaking lattice distortion as a secondary order.
The phenomena of antisymmetric magnetoresistance and the planar Hall effect are deeply entwined with ferromagnetism. The intrinsic magnetization of the ordered state permits these unusual and rarely ...observed manifestations of Onsager's theorem when time reversal symmetry is broken at zero applied field. Here we study two classes of ferromagnetic materials, rare-earth magnets with high intrinsic coercivity and antiferromagnetic pyrochlores with strongly-pinned ferromagnetic domain walls, which both exhibit antisymmetric magnetoresistive behavior. By mapping out the peculiar angular variation of the antisymmetric galvanomagnetic response with respect to the relative alignments of the magnetization, magnetic field, and electrical current, we experimentally distinguish two distinct underlying microscopic mechanisms: namely, spin-dependent scattering of a Zeeman-shifted Fermi surface and anomalous electron velocities. Our work demonstrates that the anomalous electron velocity physics typically associated with the anomalous Hall effect is prevalent beyond the ρ
(H
) channel, and should be understood as a part of the general galvanomagnetic behavior.
Background
The aim of this study was to investigate the prevalence of epidemiologic and physician‐diagnosed pollen‐induced AR (PiAR) in the grasslands of northern China and to study the impact of the ...intensity and time of pollen exposure on PiAR prevalence.
Methods
A multistage, clustered and proportionately stratified random sampling with a field interviewer‐administered survey study was performed together with skin prick tests (SPT) and measurements of the daily pollen count.
Results
A total of 6043 subjects completed the study, with a proportion of 32.4% epidemiologic AR and 18.5% PiAR. The prevalence was higher in males than females (19.6% vs 17.4%, P = .024), but no difference between the two major residential and ethnic groups (Han and Mongolian) was observed. Subjects from urban areas showed higher prevalence of PiAR than rural areas (23.1% vs 14.0%, P < .001). Most PiAR patients were sensitized to two or more pollens (79.4%) with artemisia, chenopodium, and humulus scandens being the most common pollen types, which were similarly found as the top three sensitizing pollen allergens by SPT. There were significant regional differences in the prevalence of epidemiologic AR (from 18.6% to 52.9%) and PiAR (from 10.5% to 31.4%) among the six areas investigated. PiAR symptoms were positively associated with pollen counts, temperature, and precipitation (P < .05), but negatively with wind speed and pressure P < .05).
Conclusion
Pollen‐induced AR (PiAR) prevalence in the investigated region is extremely high due to high seasonal pollen exposure, which was influenced by local environmental and climate conditions.
We use the Nernst effect to delineate the boundary of the pseudogap phase in the temperature-doping phase diagram of hole-doped cuprate superconductors. New data for the Nernst coefficient ν(T) of ...YBa2Cu3Oy (YBCO), La1.8−xEu0.2SrxCuO4 (Eu-LSCO), and La1.6−xNd0.4SrxCuO4 (Nd-LSCO) are presented and compared with previously published data on YBCO, Eu-LSCO, Nd-LSCO, and La2−xSrxCuO4 (LSCO). The temperature Tν at which ν/T deviates from its high-temperature linear behavior is found to coincide with the temperature at which the resistivity ρ(T) deviates from its linear-T dependence, which we take as the definition of the pseudogap temperature T★-in agreement with the temperature at which the antinodal spectral gap detected in angle-resolved photoemission spectroscopy (ARPES) opens. We track T★ as a function of doping and find that it decreases linearly vs p in all four materials, having the same value in the three LSCO-based cuprates, irrespective of their different crystal structures. At low p,T★ is higher than the onset temperature of the various orders observed in underdoped cuprates, suggesting that these orders are secondary instabilities of the pseudogap phase. A linear extrapolation of T★(p) to p=0 yields T★(p→0)≃TN(0), the Néel temperature for the onset of antiferromagnetic order at p=0, suggesting that there is a link between pseudogap and antiferromagnetism. With increasing p,T★(p) extrapolates linearly to zero at p≃pc2, the critical doping below which superconductivity emerges at high doping, suggesting that the conditions which favor pseudogap formation also favor pairing. We also use the Nernst effect to investigate how far superconducting fluctuations extend above the critical temperature Tc, as a function of doping, and find that a narrow fluctuation regime tracks Tc, and not T★. This confirms that the pseudogap phase is not a form of precursor superconductivity, and fluctuations in the phase of the superconducting order parameter are not what causes Tc to fall on the underdoped side of the Tc dome.
•The growth protocol for MnBi2Te4 and related compounds by vapor transport technique.•A new materials synthesis approach to defect engineering the intrinsic magnetic topological insulators.•Criteria ...for crystal screening before device fabrication.
Motivated by fine tuning of the magnetic and topological properties of MnBi2Te4 via defect engineering, in this work, we report the crystal growth of MnBi2Te4 and related compounds using vapor transport method and crystal characterization by measuring elemental ratio, magnetic and transport properties, and scanning tunneling microscopy. For the growth of MnBi2Te4 single crystals, I2, MnI2, MnCl2, TeCl4, and MoCl5 are all effective transport agents; chemical transportation occurs faster in the presence of iodides than chlorides. We further successfully grow MnSb2Te4, MnBi2−xSbxTe4, and Sb-doped MnBi4Te7 crystals. A small temperature gradient< 20∘C between the hot and cold ends of the growth ampoule is critical for the successful crystal growth of MnBi2Te4 and related compounds. Compared to flux grown crystals, vapor transported crystals tend to be Mn stoichiometric, and Sb-bearing compositions have more Mn/Sb site mixing. The vapor transport growth provides a new materials synthesis approach to fine tune the magnetic and topological properties of these intrinsic magnetic topological insulators where controlling defects is vital.
In this research, samples of the H13 steel, a commonly used hot work tool steel in the die/mould manufacturing industry, were additively manufactured using selective laser melting (SLM). Their ...as-built microstructures were characterised in detail using transmission electron microscopy (TEM) and compared with that of the conventionally manufactured H13 (as-supplied). SLM resulted in the formation of martensite and also its partial decomposition into fine α-Fe and Fe
3
C precipitates along with retained austenite. TEM analyses further revealed that the lattice of the resulting α-Fe phase is slightly distorted due to enhanced Cr, Mo and V contents. Substantially high residual stresses in the range of 940–1420 MPa were detected in the as-built H13 samples compared with its yield strength of ~1650 MPa. In addition, it was identified that the high residual stress existed from just about two additive layers (100 µm) above the substrate along the build direction. The high residual stresses were mainly attributed to the martensitic transformation that occurred during SLM. The research findings of this study suggest that the substantially high residual stresses can be easily problematic in the AM of intricate H13 dies or moulds by SLM.
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