Ultrafast magnetization enhancement via the dynamic spin-filter effect of type-II Weyl nodes in a kagome ferromagnet

The magnetic type-II Weyl semimetal (MWSM) Co3Sn2S2 has recently been found to host a variety of remarkable phenomena including surface Fermi-arcs, giant anomalous Hall effect, and negative flat band magnetism. However, the dynamic magnetic properties remain relatively unexplored. Here, we investigate the ultrafast spin dynamics of Co3Sn2S2 crystal using time-resolved magneto-optical Kerr effect and reflectivity spectroscopies. We observe a transient magnetization behavior, consisting of spin-flipping dominated fast demagnetization, slow demagnetization due to overall half-metallic electronic structures, and an unexpected ultrafast magnetization enhancement lasting hundreds of picoseconds upon femtosecond laser excitation. By combining temperature-, pump fluence-, and pump polarization-dependent measurements, we unambiguously demonstrate the correlation between the ultrafast magnetization enhancement and the Weyl nodes. Our theoretical modelling suggests that the excited electrons are spin-polarized when relaxing, leading to the enhanced spin-up density of states near the Fermi level and the consequently unusual magnetization enhancement. Our results reveal the unique role of the Weyl properties of Co3Sn2S2 in femtosecond laser-induced spin dynamics.

Diagnostic and prognostic value of parameters of erector spinae in patients with uremic sarcopenia

AIM

This study aimed to investigate whether computed tomography (CT)-measured erector spinae parameters (ESPs) have diagnostic, severity assessment, and prognostic predictive value in uremic sarcopenia (US).

MATERIALS AND METHODS

A total of 202 uremic patients were enrolled and divided into two groups: a control group and a sarcopenia group. Sarcopenia was classified into two types: severe and nonsevere. The area, volume, and density of the erector spinae (ES) were measured using chest CT images, and the relevant ESP, including the erector spinae index (ESI), total erector spinae volume (TESV), erector spinae density (ESD), and erector spinae gauge (ESG) were calculated. The occurrence of adverse events was followed-up for 36 months. The diagnostic value and severity of US were determined using the receiver operating characteristic (ROC) curve. Survival curves diagnosed using CT were plotted and compared with the curve drawn using the gold standard. Cox regression analysis was used to identify independent risk factors associated with survival in US.

RESULTS

With an area under the curve (AUC) of 0.840 and 0.739, the combined ESP has diagnostic value and the ability to assess the severity of US. There was no significant difference in the survival curve between the combined ESP for the diagnosis of US and the gold standard (P > 0.05). ESI is a standalone predictor of survival in patients with US.

CONCLUSION

ESP measured by CT has diagnostic values for US and its severity, as well as being a predictive value for the prognosis of US.

Manipulating hyperbolic transient plasmons in a layered semiconductor

Anisotropic materials with oppositely signed dielectric tensors support hyperbolic polaritons, displaying enhanced electromagnetic localization and directional energy flow. However, the most reported hyperbolic phonon polaritons are difficult to apply for active electro-optical modulations and optoelectronic devices. Here, we report a dynamic topological plasmonic dispersion transition in black phosphorus via photo-induced carrier injection, i.e., transforming the iso-frequency contour from a pristine ellipsoid to a non-equilibrium hyperboloid. Our work also demonstrates the peculiar transient plasmonic properties of the studied layered semiconductor, such as the ultrafast transition, low propagation losses, efficient optical emission from the black phosphorus's edges, and the characterization of different transient plasmon modes. Our results may be relevant for the development of future optoelectronic applications.

Basis-Set-Error-Free Random-Phase Approximation Correlation Energies for Atoms Based on the Sternheimer Equation

The finite basis set errors for all-electron random-phase approximation (RPA) correlation energy calculations are analyzed for isolated atomic systems. We show that, within the resolution-of-identity (RI) RPA framework, the major source of the basis set errors is the incompleteness of the single-particle atomic orbitals used to expand the Kohn-Sham eigenstates, instead of the auxiliary basis set (ABS) to represent the density response function χ0 and the bare Coulomb operator v. By solving the Sternheimer equation for the first-order wave function on a dense radial grid, we are able to eliminate the major error─the incompleteness error of the single-particle atomic basis set─for atomic RPA calculations. The error stemming from a finite ABS can be readily rendered vanishingly small by increasing the size of the ABS, or by iteratively determining the eigenmodes of the χ0v operator. The variational property of the RI-RPA correlation energy can be further exploited to optimize the ABS in order to achieve fast convergence of the RI-RPA correlation energy. These numerical techniques enable us to obtain basis-set-error-free RPA correlation energies for atoms, and in this work, such energies for atoms from H to Kr are presented. The implications of the numerical techniques developed in the present work for addressing the basis set issue for molecules and solids are discussed.

Twist-Induced Modification in the Electronic Structure of Bilayer WSe2

The recent discovery of strongly correlated phases in twisted transition-metal dichalcogenides (TMDs) highlights the significant impact of twist-induced modifications on electronic structures. In this study, we employed angle-resolved photoemission spectroscopy with submicrometer spatial resolution (μ-ARPES) to investigate these modifications by comparing valence band structures of twisted (5.3°) and nontwisted (AB-stacked) bilayer regions within the same WSe2 device. Relative to the nontwisted region, the twisted area exhibits pronounced moiré bands and ∼90 meV renormalization at the Γ-valley, substantial momentum separation between different layers, and an absence of flat bands at the K-valley. We further simulated the effects of lattice relaxation, which can flatten the Γ-valley edge but not the K-valley edge. Our results provide a direct visualization of twist-induced modifications in the electronic structures of twisted TMDs and elucidate their valley-dependent responses to lattice relaxation.

Postoperative pulmonary complications in older patients undergoing elective surgery with a supraglottic airway device or tracheal intubation

The two most commonly used airway management techniques during general anaesthesia are supraglottic airway devices and tracheal tubes. In older patients undergoing elective non-cardiothoracic surgery under general anaesthesia with positive pressure ventilation, we hypothesised that a composite measure of in-hospital postoperative pulmonary complications would be less frequent when a supraglottic airway device was used compared with a tracheal tube. We studied patients aged ≥ 70 years in 17 clinical centres. Patients were allocated randomly to airway management with a supraglottic airway device or a tracheal tube. Between August 2016 and April 2020, 2900 patients were studied, of whom 2751 were included in the primary analysis (1387 with supraglottic airway device and 1364 with a tracheal tube). Pre-operatively, 2431 (88.4%) patients were estimated to have a postoperative pulmonary complication risk index of 1-2. Postoperative pulmonary complications, mostly coughing, occurred in 270 of 1387 patients (19.5%) allocated to a supraglottic airway device and 342 of 1364 patients (25.1%) assigned to a tracheal tube (absolute difference -5.6% (95%CI -8.7 to -2.5), risk ratio 0.78 (95%CI 0.67-0.89); p < 0.001). Among otherwise healthy older patients undergoing elective surgery under general anaesthesia with intra-operative positive pressure ventilation of their lungs, there were fewer postoperative pulmonary complications when the airway was managed with a supraglottic airway device compared with a tracheal tube.

Large Anomalous Nernst Effects at Room Temperature in Fe3 Pt Thin Films

Heat current in ferromagnets can generate a transverse electric voltage perpendicular to magnetization, known as anomalous Nernst effect (ANE). ANE originates intrinsically from the combination of large Berry curvature and density of states near the Fermi energy. It shows technical advantages over the conventional longitudinal Seebeck effect in converting waste heat to electricity due to its unique transverse geometry. However, materials showing giant ANE remain to be explored. Herein,  a large ANE thermopower of Syx ≈ 2 µV K-1 at room temperature in ferromagnetic Fe3 Pt epitaxial films is reported, which also show a giant transverse thermoelectric conductivity of αyx ≈ 4 A K-1  m-1 and a remarkable coercive field of 1300 Oe. The theoretical analysis reveals that the strong spin-orbit interaction in addition to the hybridization between Pt 5d and Fe 3d electrons leads to a series of distinct energy gaps and large Berry curvature in the Brillouin zone, which is the key for the large ANE. These results highlight the important roles of both Berry curvature and spin-orbit coupling in achieving large ANE at zero magnetic field, providing pathways to explore materials with giant transverse thermoelectric effect without an external magnetic field.

Gate-Tunable Multiband Transport in ZrTe5 Thin Devices

Interest in ZrTe₅ has been reinvigorated in recent years owing to its potential for hosting versatile topological electronic states and intriguing experimental discoveries. However, the mechanism of many of its unusual transport behaviors remains controversial: for example, the characteristic peak in the temperature-dependent resistivity and the anomalous Hall effect. Here, through employing a clean dry-transfer fabrication method in an inert environment, we successfully obtain high-quality ZrTe₅ thin devices that exhibit clear dual-gate tunability and ambipolar field effects. Such devices allow us to systematically study the resistance peak as well as the Hall effect at various doping densities and temperatures, revealing the contribution from electron-hole asymmetry and multiple-carrier transport. By comparing with theoretical calculations, we suggest a simplified semiclassical two-band model to explain the experimental observations. Our work helps to resolve the longstanding puzzles on ZrTe₅ and could potentially pave the way for realizing novel topological states in the two-dimensional limit.

Large Spin Hall Conductivity and Excellent Hydrogen Evolution Reaction Activity in Unconventional PtTe1.75 Monolayer

Two-dimensional (2D) materials have gained lots of attention due to the potential applications. In this work, we propose that based on first-principles calculations, the (2 × 2) patterned PtTe₂ monolayer with kagome lattice formed by the well-ordered Te vacancy (PtTe_1.75) hosts large and tunable spin Hall conductivity (SHC) and excellent hydrogen evolution reaction (HER) activity. The unconventional nature relies on the A1 @ 1b band representation of the highest valence band without spin-orbit coupling (SOC). The large SHC comes from the Rashba SOC in the noncentrosymmetric structure induced by the Te vacancy. Even though it has a metallic SOC band structure, the ℤ₂ invariant is well defined because of the existence of the direct bandgap and is computed to be nontrivial. The calculated SHC is as large as 1.25 × 10³ ℏ e (Ω cm)^-1 at the Fermi level (E_F ). By tuning the chemical potential from E_F - 0.3 to E_F + 0.3 eV, it varies rapidly and monotonically from -1.2 × 10³ to 3.1 × 1 0 3 ℏ e Ω   cm - 1 . In addition, we also find that the Te vacancy in the patterned monolayer can induce excellent HER activity. Our results not only offer a new idea to search 2D materials with large SHC, i.e., by introducing inversion-symmetry breaking vacancies in large SOC systems, but also provide a feasible system with tunable SHC (by applying gate voltage) and excellent HER activity.

Topological Crystalline Insulator Candidate ErAsS with Hourglass Fermion and Magnetic-Tuned Topological Phase Transition

Topological crystalline insulators (TCIs) with hourglass fermion surface state have attracted a lot of attention and are further enriched by crystalline symmetries and magnetic order. Here, the emergence of hourglass fermion surface state and exotic phases in the newly discovered, air-stable ErAsS single crystals are shown. In the paramagnetic phase, ErAsS is expected to be a TCI with hourglass fermion surface state protected by the nonsymmorphic symmetry. Dirac-cone-like bands and nearly linear dispersions in large energy range are experimentally observed, consistent well with theoretical calculations. Below T_N  ≈ 3.27 K, ErAsS enters a collinear antiferromagnetic state, which is a trivial insulator breaking the time-reversal symmetry. An intermediate incommensurate magnetic state appears in a narrow temperature range (3.27-3.65 K), exhibiting an abrupt change in magnetic coupling. The results reveal that ErAsS is an experimentally available TCI candidate and provide a unique platform to understand the formation of hourglass fermion surface state and explore magnetic-tuned topological phase transitions.

Flat-Band-Induced Anomalous Anisotropic Charge Transport and Orbital Magnetism in Kagome Metal CoSn

For solids, the dispersionless flat band has long been recognized as an ideal platform for achieving intriguing quantum phases. However, experimental progress in revealing flat-band physics has so far been achieved mainly in artificially engineered systems represented as magic-angle twisted bilayer graphene. Here, we demonstrate the emergence of flat-band-dominated anomalous transport and magnetic behaviors in CoSn, a paramagnetic kagome-lattice compound. By combination of angle-resolved photoemission spectroscopy measurements and first-principles calculations, we reveal the existence of a kagome-lattice-derived flat band right around the Fermi level. Strikingly, the resistivity within the kagome lattice plane is more than one order of magnitude larger than the interplane one, in sharp contrast with conventional (quasi-) two-dimensional layered materials. Moreover, the magnetic susceptibility under the out-of-plane magnetic field is found to be much smaller as compared with the in-plane case, which is revealed to be arising from the introduction of a unique orbital diamagnetism. Systematic analyses reveal that these anomalous and giant anisotropies can be reasonably attributed to the unique properties of flat-band electrons, including large effective mass and self-localization of wave functions. Our results broaden the already fascinating flat-band physics, and demonstrate the feasibility of exploring them in natural solid-state materials in addition to artificial ones.

High-harmonic generation in Weyl semimetal β-WP2 crystals

As a quantum material, Weyl semimetal has a series of electronic-band-structure features, including Weyl points with left and right chirality and corresponding Berry curvature, which have been observed in experiments. These band-structure features also lead to some unique nonlinear properties, especially high-order harmonic generation (HHG) due to the dynamic process of electrons under strong laser excitation, which has remained unexplored previously. Herein, we obtain effective HHG in type-II Weyl semimetal β-WP2 crystals, where both odd and even orders are observed, with spectra extending into the vacuum ultraviolet region (190 nm, 10th order), even under fairly low femtosecond laser intensity. In-depth studies have interpreted that odd-order harmonics come from the Bloch electron oscillation, while even orders are attributed to Bloch oscillations under the "spike-like" Berry curvature at Weyl points. With crystallographic orientation-dependent HHG spectra, we further quantitatively retrieved the electronic band structure and Berry curvature of β-WP2. These findings may open the door for exploiting metallic/semimetallic states as solid platforms for deep ultraviolet radiation and offer an all-optical and pragmatic solution to characterize the complicated multiband electronic structure and Berry curvature of quantum topological materials.

Facet Engineering to Regulate Surface States of Topological Crystalline Insulator Bismuth Rhombic Dodecahedrons for Highly Energy Efficient Electrochemical CO2 Reduction

Bismuth (Bi) is a topological crystalline insulator (TCI), which has gapless topological surface states (TSSs) protected by a specific crystalline symmetry that strongly depends on the facet. Bi is also a promising electrochemical CO₂ reduction reaction (ECO₂ RR) electrocatalyst for formate production. In this study, single-crystalline Bi rhombic dodecahedrons (RDs) exposed with (104) and (110) facets are developed. The Bi RDs demonstrate a very low overpotential and high selectivity for formate production (Faradic efficiency >92.2%) in a wide partial current density range from 9.8 to 290.1 mA cm^-2 , leading to a remarkably high full-cell energy efficiency (69.5%) for ECO₂ RR. The significantly reduced overpotential is caused by the enhanced *OCHO adsorption on the Bi RDs. The high selectivity of formate can be ascribed to the TSSs and the trivial surface states opening small gaps in the bulk gap on Bi RDs, which strengthens and stabilizes the preferentially adsorbed *OCHO and mitigates the competing adsorption of *H during ECO₂ RR. This study describes a promising application of Bi RDs for high-rate formate production and high-efficiency energy storage of intermittent renewable electricity. Optimizing the geometry of TCIs is also proposed as an effective strategy to tune the TSSs of topological catalysts.

High-Throughput Screening of Element-Doped Carbon Nanotubes Toward an Optimal One-Dimensional Superconductor

In order to search for optimal one-dimensional (1D) superconductors with a high transition temperature (T_c), we performed high-throughput computation on the phonon dispersion, electron-phonon coupling (EPC), and superconducting properties of (5,0), (3,3), and element-doped (3,3) carbon nanotubes (CNTs) based on first-principles calculations. We find that the CNT (5,0) is superconductive with T_c of 7.9 K, while the (3,3) CNT has no superconductivity. However, by high-throughput screening of about 50 elements in the periodic table, we identified that 14 elemental dopants can make the (3,3) CNT dynamically stable and superconducting. The high T_c ≈ 28 K suggests that the Si-doped (3,3) CNT is an excellent one-dimensional (1D) superconductor. In addition, the Al-, In-, and La-doped (3,3) CNTs are also great 1D superconductor candidates with a T_c of about 18, 17, and 29 K, respectively. These results may inspire the synthesis and discovery of optimal high-T_c 1D superconductors experimentally.

Metallization of Quantum Material GaTa4Se8 at High Pressure

Pressure is a unique thermodynamic variable to explore the phase competitions and novel phases inaccessible at ambient conditions. The resistive switching material GaTa₄Se₈ displays several quantum phases under pressure, such as a J_eff = 3/2 Mott insulator, a correlated quantum magnetic metal, and d-wave topological superconductivity, which has recently drawn considerable interest. Using high-pressure Raman spectroscopy, X-ray diffraction, extended X-ray absorption, transport measurements, and theoretical calculations, we reveal a complex phase diagram for GaTa₄Se₈ at pressures exceeding 50 GPa. In this previously unattained pressure regime, GaTa₄Se₈ ranges from a Mott insulator to a metallic phase and exhibits superconducting phases. In contrast to previous studies, we unveil a hidden correlation between the structural distortion and band gap prior to the insulator-to-metal transition, and the metallic phase shows superconductivity with structural and magnetic properties that are distinctive from the lower-pressure phase. These discoveries highlight that GaTa₄Se₈ is a unique material to probe novel quantum phases from a structural, metallicity, magnetism, and superconductivity perspective.

High-throughput screening for Weyl semimetals with S4 symmetry

Based on irreducible representations (or symmetry eigenvalues) and compatibility relations (CR), a material can be predicted to be a topological/trivial insulator (satisfying CR) or a topological semimetal (violating CR). However, Weyl semimetals (WSMs) usually go beyond this symmetry-based strategy. In other words, Weyl nodes could emerge in a material, no matter if its occupied bands satisfy CR, or if the symmetry indicators are zero. In this work, we propose a new topological invariant χ for the systems with S₄ symmetry (i.e., the improper rotation S₄(≡IC_4z) is a proper fourfold rotation (C_4z) followed by inversion (I)), which can be used to diagnose the WSM phase. Moreover, χ can be easily computed through the one-dimensional Wilson-loop technique. By applying this method to the high-throughput screening in our first-principles calculations, we predict a lot of WSMs in both nonmagnetic and magnetic compounds. Various interesting properties (e.g., magnetic frustration effects, superconductivity and spin-glass order, etc.) are found in predicted WSMs, which provide realistic platforms for future experimental study of the interplay between Weyl fermions and other exotic states.

Observation and control of the weak topological insulator state in ZrTe5

A quantum spin Hall (QSH) insulator hosts topological states at the one-dimensional (1D) edge, along which backscattering by nonmagnetic impurities is strictly prohibited. Its 3D analogue, a weak topological insulator (WTI), possesses similar quasi-1D topological states confined at side surfaces. The enhanced confinement could provide a route for dissipationless current and better advantages for applications relative to strong topological insulators (STIs). However, the topological side surface is usually not cleavable and is thus hard to observe. Here, we visualize the topological states of the WTI candidate ZrTe5 by spin and angle-resolved photoemission spectroscopy (ARPES): a quasi-1D band with spin-momentum locking was revealed on the side surface. We further demonstrate that the bulk band gap is controlled by external strain, realizing a more stable WTI state or an ideal Dirac semimetal (DS) state. The highly directional spin-current and the tunable band gap in ZrTe5 will provide an excellent platform for applications.

Insight of the Influence of Magnetic-Field Direction on Magneto-Plasmonic Interfaces for Tuning Photocatalytical Performance of Semiconductors

Boosting photocatalytic performance via external fields is an alternative and effective solution for improving the application performance of existing photocatalysts. Herein, using α-Fe₂O₃-decorated TiO₂ nanotube arrays as a model, we demonstrate the influence of magnetic field (MF)-direction on the photogenerated charge-carrier transfer behavior at plasmonic metal/semiconductor interfaces. For the first time, the photocatalytic activity is also found to correlate with the plasmonic metal species while applying an external MF. As verified by first-principles calculations, the spin-orbit coupling of metal contributes to the charge-carrier transfer. To highlight the anisotropic MF-tuning effect in practical applications, the as-prepared architecture is applied for photocatalysis-triggered drug delivery. The delivery rate can be remarkably accelerated by ∼38% under a tiny MF (0.4 T) with the proper direction. The findings in this research may provide new insight into designing semiconductor architectures for boosting the photocatalytical performance in an external MF.

Electronic structures and topological properties in nickelates Ln n+1NinO2n+2

After the significant discovery of the hole-doped nickelate compound Nd0.8Sr0.2NiO2, analyses of the electronic structure, orbital components, Fermi surfaces and band topology could be helpful to understand the mechanism of its superconductivity. Based on first-principle calculations, we find that Ni $3d_{x^2-y^2}$ states contribute the largest Fermi surface. The $Ln 5d_{3z^2-r^2}$ states form an electron pocket at Γ, while 5dxy states form a relatively bigger electron pocket at A. These Fermi surfaces and symmetry characteristics can be reproduced by our two-band model, which consists of two elementary band representations: B1g@1a ⊕ A1g@1b. We find that there is a band inversion near A, giving rise to a pair of Dirac points along M-A below the Fermi level upon including spin-orbit coupling. Furthermore, we perform density functional theory based Gutzwiller (DFT+Gutzwiller) calculations to treat the strong correlation effect of Ni 3d orbitals. In particular, the bandwidth of $3d_{x^2-y^2}$ has been renormalized largely. After the renormalization of the correlated bands, the Ni 3dxy states and the Dirac points become very close to the Fermi level. Thus, a hole pocket at A could be introduced by hole doping, which may be related to the observed sign change of the Hall coefficient. By introducing an additional Ni 3dxy orbital, the hole-pocket band and the band inversion can be captured in our modified model. Besides, the nontrivial band topology in the ferromagnetic two-layer compound La3Ni2O6 is discussed and the band inversion is associated with Ni $3d_{x^2-y^2}$ and La 5dxy orbitals.

Emergence of Nontrivial Low-Energy Dirac Fermions in Antiferromagnetic EuCd2 As2

Parity-time symmetry plays an essential role for the formation of Dirac states in Dirac semimetals. So far, all of the experimentally identified topologically nontrivial Dirac semimetals (DSMs) possess both parity and time reversal symmetry. The realization of magnetic topological DSMs remains a major issue in topological material research. Here, combining angle-resolved photoemission spectroscopy with density functional theory calculations, it is ascertained that band inversion induces a topologically nontrivial ground state in EuCd₂ As₂ . As a result, ideal magnetic Dirac fermions with simplest double cone structure near the Fermi level emerge in the antiferromagnetic (AFM) phase. The magnetic order breaks time reversal symmetry, but preserves inversion symmetry. The double degeneracy of the Dirac bands is protected by a combination of inversion, time-reversal, and an additional translation operation. Moreover, the calculations show that a deviation of the magnetic moments from the c-axis leads to the breaking of C3 rotation symmetry, and thus, a small bandgap opens at the Dirac point in the bulk. In this case, the system hosts a novel state containing three different types of topological insulator: axion insulator, AFM topological crystalline insulator (TCI), and higher order topological insulator. The results provide an enlarged platform for the quest of topological Dirac fermions in a magnetic system.

Magnetization-Induced Band Shift in Ferromagnetic Weyl Semimetal Co_{3}Sn_{2}S_{2}

The discovery of magnetic Weyl semimetal (magnetic WSM) in Co_{3}Sn_{2}S_{2} has triggered great interest for abundant fascinating phenomena induced by band topology conspiring with the magnetism. Understanding how the magnetization affects the band structure can give us a deeper comprehension of the magnetic WSMs and guide us for the innovation in applications. Here, we systematically study the temperature-dependent optical spectra of ferromagnetic WSM Co_{3}Sn_{2}S_{2} experimentally and simulated by first-principles calculations. Our results indicate that the many-body correlation effect due to Co 3d electrons leads to the renormalization of electronic kinetic energy by a factor about 0.43, which is moderate, and the description within density functional theory is suitable. As the temperature drops down, the magnetic phase transition happens, and the magnetization drives the band shift through exchange splitting. The optical spectra can well detect these changes, including the transitions sensitive and insensitive to the magnetization, and those from the bands around the Weyl nodes. The results support that, in magnetic WSM Co_{3}Sn_{2}S_{2}, the bands that contain Weyl nodes can be tuned by magnetization with temperature change.

Magnetic Semimetals and Quantized Anomalous Hall Effect in EuB_{6}

Exploration of the novel relationship between magnetic order and topological semimetals has received enormous interest in a wide range of both fundamental and applied research. Here we predict that "soft" ferromagnetic material EuB_{6} can achieve multiple topological semimetal phases by simply tuning the direction of the magnetic moment. Explicitly, EuB_{6} is a topological nodal-line semimetal when the moment is aligned along the [001] direction, and it evolves into a Weyl semimetal with three pairs of Weyl points by rotating the moment to the [111] direction. Interestingly, we identify a composite semimetal phase featuring the coexistence of a nodal line and Weyl points with the moment in the [110] direction. Topological surface states and anomalous Hall conductivity, which are sensitive to the magnetic order, have been computed and are expected to be experimentally observable. Large-Chern-number quantum anomalous Hall effect can be realized in its [111]-oriented quantum-well structures.

Chiral terahertz wave emission from the Weyl semimetal TaAs

Weyl semimetals host chiral fermions with distinct chiralities and spin textures. Optical excitations involving those chiral fermions can induce exotic carrier responses, and in turn lead to novel optical phenomena. Here, we discover strong coherent terahertz emission from Weyl semimetal TaAs, which is demonstrated as a unique broadband source of the chiral terahertz wave. The polarization control of the THz emission is achieved by tuning photoexcitation of ultrafast photocurrents via the photogalvanic effect. In the near-infrared regime, the photon-energy dependent nonthermal current due to the predominant circular photogalvanic effect can be attributed to the radical change of the band velocities when the chiral Weyl fermions are excited during selective optical transitions between the tilted anisotropic Weyl cones and the massive bulk bands. Our findings provide a design concept for creating chiral photon sources using quantum materials and open up new opportunities for developing ultrafast opto-electronics using Weyl physics.

Atomically Resolved Edge States on a Layered Ferroelectric Oxide

The emerging surface/edge electronic phases driven by broken symmetry effects have attracted great attention in low-dimensional electronic systems. However, experimental proof on their existence in ferroelectric oxides at the atomic scale is still missing. In this work, metallic surface states are observed on layered Bi₂WO₆ by scanning tunneling microscopy/spectroscopy. Differential conductance is remarkably enhanced near the step edge compared with that on the terrace, forming a one-dimensional edge state. Density functional theory calculations verify that symmetry breaking at the surface determines the electronic structures and O 2p orbitals contribute the most to the density of states around the Fermi level. Our discovery provides a new strategy toward the hidden phases on other correlated oxide surfaces.

Quasiparticle interference evidence of the topological Fermi arc states in chiral fermionic semimetal CoSi

Chiral fermions in solid state feature "Fermi arc" states, connecting the surface projections of the bulk chiral nodes. The surface Fermi arc is a signature of nontrivial bulk topology. Unconventional chiral fermions with an extensive Fermi arc traversing the whole Brillouin zone have been theoretically proposed in CoSi. Here, we use scanning tunneling microscopy/spectroscopy to investigate quasiparticle interference at various terminations of a CoSi single crystal. The observed surface states exhibit chiral fermion-originated characteristics. These reside on (001) and (011) but not (111) surfaces with p-rotation symmetry, spiral with energy, and disperse in a wide energy range from ~-200 to ~+400 mV. Owing to the high-energy and high-space resolution, a spin-orbit coupling-induced splitting of up to ~80 mV is identified. Our observations are corroborated by density functional theory and provide strong evidence that CoSi hosts the unconventional chiral fermions and the extensive Fermi arc states.

Higher-Order Topology of the Axion Insulator EuIn_{2}As_{2}

Based on first-principles calculations and symmetry analysis, we propose that EuIn_{2}As_{2} is a long-awaited axion insulator with antiferromagnetic (AFM) long-range order. Characterized by the parity-based invariant Z_{4}=2, the topological magnetoelectric effect is quantized with θ=π in the bulk, with a band gap as large as 0.1 eV. When the staggered magnetic moments of the AFM phase are along the a or b axis, it is also a topological crystalline insulator phase with gapless surface states emerging on (100), (010), and (001) surfaces. When the magnetic moments are along the c axis, both the (100) and (001) surfaces are gapped, and the material can also be viewed as a high-order topological insulator with one-dimensional chiral states existing on the hinges between those gapped surfaces. We have calculated both the topological surface states and the hinge state in different phases of the system, respectively, which can be detected by angle-resolved photoemission spectroscopy or STM experiments.

Three-Dimensional Crystalline Modification of Graphene in all-sp2 Hexagonal Lattices with or without Topological Nodal Lines

The discovery of fullerenes, nanotubes, and graphene has ignited tremendous interest in exploring additional all-sp² carbon networks with novel properties. Here we identify by ab initio calculations a new series of three-dimensional crystalline modification of carbon in all-sp² bonding networks that comprise trigonal polycyclic benzenoid nanoflakes in a 2 n² ( n ≥ 4) atom hexagonal cell. The resulting 32-, 50-, 72-, and 98-atom structures (termed as tr32, tr50, tr72, and tr98) in trigonal ( P3̅ m1) symmetry are characterized as the crystalline modification of ( n × n × 1)-graphene in AA stacking, which are energetically more stable than or comparable to the solid fcc-C₆₀ and (5,5) carbon nanotube. Electronic band structure calculations show that tr72 without 2 d (1/3, 2/3, z) symmetric carbon atoms is a semiconductor, while tr32, tr50, and tr98 with 2 d carbon atoms are topological nodal-line semimetals comprising nodal lines on the H-K-H' edge in the hexagonal Brillouin zone, as a three-dimensional extension of the Dirac point at the K-point in two-dimensional graphene. The present findings establish an additional crystalline modification of graphene in the all-sp² carbon allotrope family and offer insights into its outstanding structural and electronic properties.

[Analysis of 9 cases of nodular type of pulmonary cryptococcosis with coexisting lung cancer confirmed by pathological examinations]

Objective: To describe the characteristics of the nodular type of pulmonary cryptococcosis (PC) with coexisting lung cancer. Methods: A total of 9 cases of PC with coexisting lung cancer, admitted to Fuzhou Pulmonary Hospital of Fujian from 1st January 2009 to 31th December 2016, and confirmed by pathological examinations, were studied and the related literature were reviewed. Results: The patients consisted of 1 male and 8 females, with a mean age of (53±10) years (range, 38 to 68 years). Four patients (44.4%) had underlying diseases, 3 with diabetes mellitus and 1 with gastric cancer surgery. The main clinical manifestations of most cases were cough and phlegm. The lesions of PC on chest CT were mostly solitary or multiple nodules with a diameter < 1 cm, and the lesions of carcinoma were shown as solitary nodules with a variety of signs suggestive of malignancy. All the patients were confirmed to have concomitant PC and lung adenocarcinoma by pathological examinations. Lung cancer stage was early (Tis and Ⅰ-Ⅱ) in 88.9 % (8 cases) of the cases. All the patients received surgery and postoperative medical therapy. The prognosis was relatively good in most of them except 1 case with death due to lung cancer metastasis and 1 case with lung cancer recurrence. Conclusions: Coexistence of PC and lung cancer is rare and the clinical symptoms are not specific. When PC coexists with carcinoma and manifests as pulmonary nodule, it mimics malignant lesions and is extremely easy to be misdiagnosed. Therefore PC must be considered in the differential diagnosis of pulmonary nodules.

[Endoscopicretrograde cholangio-pancreatography management of long-term complications after pancreaticoduodenectomy]

Objective: To investigate the feasibility and effectiveness of endoscopicretrograde cholangio-pancreatography(ERCP)in the management of long-term complications after pancreaticoduodenectomy. Methods: From January 2009 to July 2018, the clinical data of 62 patients with biliary or pancreatic long-term complications after pancreatoduodenectomy were reviewed at Department of General Surgery, and the corresponding ERCP were carried out in the multi-disciplinary cooperation.There were 39 males and 24 females.The age was 56.5 years(aging from 13 to 76 years). The time of treatment was 3 months to 20 years after pancreatoduodenectomy.The long-term biliopancreatic complications after pancreatoduodenectomy included 51 cases of biliary calculi, 42 cases of bilioenteric anastomotic stenosis with proximal bile duct dilatation, and 11 cases of pancreaticointestinal anastomosis stenosis with distal pancreatic duct dilatation.All patients received conventional duodenoscopy or single-balloon enteroscopy assisted ERCP under general anesthesia. Results: A total of 95 ERCP were performed in 62 patients, averaging 1.5 times per case.The long-term complications of cholangiopancreatic after pancreatoduodenectomy(ERCP indications) included 56 times of bile duct stones(58.9%), 45 times of bilioenteric anastomatic stricture(47.4%), 11 times of recurrent pancreatitis(11.6%), 6 cases(6.3%) of bilioenteric anastomatic foreign body, 3 times of intrahepatic bile duct stenosis(3.2%). Among the 95 times, 82 times(86.3%) achieved endoscopic endoscopy, 76 times(80.0%) were diagnosed successfully, and 72 times(75.8%) were successfully treated with ERCP.Small intestinal perforation occurred in 1 patient undergoing duodenoscopy, and then healed by surgical repair. Conclusion: Multi-disciplinary collaboration of ERCP is safe and effective in the treatment of long-term complications after pancreaticoduodenectomy, but the long-term effect still needs further clinical follow-up.

A Wide-Range Photosensitive Weyl Semimetal Single Crystal-TaAs

Mid- and even long-infrared photodetection is highly desired for various modern optoelectronic devices, and photodetectors that operate at room temperature (RT) remain challenging and are being extensively sought. Recently, the Weyl semimetal has attracted much interest, and its Lorentz invariance can be broken to have tilted chiral Weyl cones around the Fermi level, which indicates that the photocurrent can be generated by the incident photons at arbitrarily long wavelengths. Furthermore, the atypical linear dispersion bands in Weyl cones result in high carrier mobility and quadratic energy dependence of the density of states, which can enhance the efficiency of the photocurrent and suppress thermal carriers, in addition to its favorable large absorption coefficient. In this study, a Weyl semimetal TaAs photodetecting prototype is reported, which operates at RT with an outstanding response that ranges from the visible to the long-infrared range. This study indicates that the Weyl semimetal TaAs should boost the development of modern optoelectronics and photonics.

Minimizing the Sample Sizes of Clinical Trials on Preclinical and Early Symptomatic Stage of Alzheimer Disease

BACKGROUND

Clinical trials of investigational drugs for Alzheimer disease (AD) increasingly focus on the prodromal (symptomatic) stage of the illness and now its preclinical (asymptomatic) stage. Sensitive and specific cognitive and functional endpoints are needed to track subtle cognitive and functional changes in the early and preclinical stages to minimize sample sizes in these trials.

OBJECTIVES

To identify informative items in a standard clinical assessment protocol and a psychometric battery that are predictive of onset of dementia symptom.

DESIGN

Longitudinal retrospective study.

SETTING

Washington University (WU) Knight Alzheimer Disease Research Center (ADRC).

PARTICIPANTS

A total of 735 individuals at least 65 years old and cognitively normal at baseline from a longitudinal clinical cohort at the WU Knight ADRC.

MEASUREMENTS

The annual clinical assessment included a wide spectrum of functional and cognitive domains; a comprehensive psychometric battery was completed about 2 weeks after the clinical evaluation. Psychometricians are blinded to the results of the clinical evaluation and to the prior performance of the participants on the psychometric tests.

RESULTS

The mean age at baseline of the 735 participants was 74.30 and 62.31% were female. 240 individuals developed prodromal dementia symptoms (consistent with mild cognitive impairment due to AD and with very mild AD dementia) during longitudinal follow-up (mean follow-up=6.79 years). Among a total of 562 items in the clinical and cognitive assessments under analysis, 292 (52%) were identified as informative because their longitudinal changes were predictive of symptomatic onset. When these items were used to form the functional and cognitive composites, the longitudinal rates of changes were free of a learning effect and captured subtle longitudinal progression prior to symptomatic onset. The rates of change were much greater right after the symptomatic onset than those from the functional and cognitive composites formed using non-informative items. Although the sample sizes for prevention trials (prior to symptomatic onset) using the informative items still yield large numbers, the sample sizes for early treatment trial (after symptomatic onset) was much smaller than those derived from all the items or from the non-informative items alone.

CONCLUSIONS

The antecedent longitudinal changes in nearly half of the items in a clinical assessment protocol and a comprehensive cognitive battery did not show statistically significant ability to predict the dementia symptom onset, and hence may be non-informative to track the preclinical functional and cognitive progression of AD. The remaining items, on the other hand, captured some of the preclinical changes prior to the symptom onset, but performed much better right after the symptom onset. Currently ongoing prevention trials on preclinical AD of elderly individuals may need to re-assess the sample sizes and statistical power.

[Choice of genetic model on Meta-analysis of genetic association studies: introduction of genetic model-free approach for Bayesian analysis]

Meta-analysis used for genetic association studies became popular among researchers, with the amount of published papers increased rapidly. In this paper, we will focus on the introduction on the selection of genetic models. Traditionally, methods used for Meta-analysis on genetic association studies was to calculate the statistics based on available genetic models which not only increasing the probability of false-positives but also making the interpretation of results more difficult. Hence, a critical step in the Meta-analysis of genetic association studies was to choose the appropriate inheritance model. The aim of this paper was to introduce the theory of Bayesian analysis regarding the genetic model-free approach, in performing the Meta-analysis for studies related to genetic associations.

Topological Nodal-Net Semimetal in a Graphene Network Structure

Topological semimetals are characterized by the nodal points in their electronic structure near the Fermi level, either discrete or forming a continuous line or ring, which are responsible for exotic properties related to the topology of bulk bands. Here we identify by ab initio calculations a distinct topological semimetal that exhibits nodal nets comprising multiple interconnected nodal lines in bulk and have two coupled drumheadlike flat bands around the Fermi level on its surface. This nodal net semimetal state is proposed to be realized in a graphene network structure that can be constructed by inserting a benzene ring into each C─C bond in the bct-C_{4} lattice or by a crystalline modification of the (5,5) carbon nanotube. These results expand the realm of nodal manifolds in topological semimetals, offering a new platform for exploring novel physics in these fascinating materials.

Double-Weyl Phonons in Transition-Metal Monosilicides

We employed ab initio calculations to identify a class of crystalline materials of MSi (M=Fe, Co, Mn, Re, Ru) having double-Weyl points in both their acoustic and optical phonon spectra. They exhibit novel topological points termed "spin-1 Weyl point" at the Brillouin zone center and "charge-2 Dirac point" at the zone corner. The corresponding gapless surface phonon dispersions are two helicoidal sheets whose isofrequency contours form a single noncontractible loop in the surface Brillouin zone. In addition, the global structure of the surface bands can be analytically expressed as double-periodic Weierstrass elliptic functions.

Noncollinear Magnetic Structure and Multipolar Order in Eu_{2}Ir_{2}O_{7}

The magnetic properties of the pyrochlore iridate material Eu_{2}Ir_{2}O_{7} (5d^{5}) have been studied based on first principles calculations, where the crystal field splitting Δ, spin-orbit coupling (SOC) λ, and Coulomb interaction U within Ir 5d orbitals all play significant roles. The ground state phase diagram has been obtained with respect to the strength of SOC and Coulomb interaction U, where a stable antiferromagnetic ground state with all-in-all-out (AIAO) spin structure has been found. In addition, another antiferromagnetic state with energy close to AIAO has also been found to be stable. The calculated nonlinear magnetization of the two stable states both have the d-wave pattern but with a π/4 phase difference, which can perfectly explain the experimentally observed nonlinear magnetization pattern. Compared with the results of the nondistorted structure, it turns out that the trigonal lattice distortion is crucial for stabilizing the AIAO state in Eu_{2}Ir_{2}O_{7}. Furthermore, besides large dipolar moments, we also find considerable octupolar moments in the magnetic states.

[Clinical application and evaluation of an early non-sedation protocol for critically ill respiratory patients]

Objective: To study the value of an early (mechanical ventilation after 24 h) non-sedation protocol for intubated, mechanically ventilated patients in the respiratory intensive care unit (RICU). Methods: Seventy intubated, mechanically ventilated patients were prospectively enrolled and randomly assigned to management with early non-sedation (intervention group; n=35) or with daily interruption of sedation (DIS) (control group; n=35). The duration of mechanical ventilation, length of the RICU and hospital stay, RICU and hospital mortality, drug consumption, RICU and hospitalization expenses, incidence of complications and adverse events and serum levels of vital organ damage and inflammatory markers after mechanical ventilation for 48 h were recorded and compared. Results: Patients in the intervention group had a shorter duration of mechanical ventilation than those in the control group [(7±5) vs (11±9) d, P<0.05] and were discharged from the RICU [(9±7) vs (18±9) d, P<0.05] and hospital earlier [(17±14) vs (29±22) d, P<0.05] than those in the control group. The doses of midazolam were significantly lower in the intervention group than in the control group [(99±104) vs (482±337) mg, P<0.05]. The RICU and hospitalization expenses were both significantly lower in the intervention group than in the control group [53(84) vs 88(173), 72(195) vs 154(234) thousand CHY, P<0.05]. In the intervention group, the occurrence rates of ventilator associated pneumonia (23% vs 46%), tracheotomy (14% vs 37%) and gastrointestinal adverse reactions (17% vs 40%) were significantly lower than those in the control group (P<0.05). No differences were recorded in RICU and hospital mortality (P>0.05). The occurrence rates of unplanned extubation and reintubation and the need for CT brain scans were similar in the 2 groups (P>0.05). The levels of cardiac, liver and renal damage markers, lactic acid and C-reactive protein were the same in both groups (P>0.05). Conclusions: The early non-sedation protocol decreased the duration of mechanical ventilation and the length of stay in the RICU and hospital, and it did not increase the incidence of complications and adverse events.

[Retrospective analysis of 117 cases of pulmonary cryptococcosis]

The clinical symptoms of PC were diverse and nonspecific. Halo sign and proximal air bronchogram are helpful for the diagnosis of PC. The outcome of most patients was satisfactory after appropriate treatment.

d Orbital Topological Insulator and Semimetal in the Antifluorite Cu2S Family: Contrasting Spin Helicities, Nodal Box, and Hybrid Surface States

We reveal a class of three-dimensional d orbital topological materials in the antifluorite Cu₂S family. Derived from the unique properties of low-energy t_2g states, their phases are solely determined by the sign of the spin-orbit coupling (SOC): topological insulator (TI) for negative SOC and topological semimetal for positive SOC, both having Dirac cone surface states but with contrasting helicities. With broken inversion symmetry, the semimetal becomes one with a nodal box consisting of butterfly-shaped nodal lines that are robust against SOC. Further breaking the tetrahedral symmetry by strain leads to an ideal Weyl semimetal with four pairs of Weyl points. Interestingly, the Fermi arcs coexist with a surface Dirac cone on the (010) surface, as required by a [Formula: see text] invariant.

From Nodal Chain Semimetal to Weyl Semimetal in HfC

Based on first-principles calculations and effective model analysis, we propose that the WC-type HfC, in the absence of spin-orbit coupling (SOC), can host a three-dimensional nodal chain semimetal state. Distinguished from the previous material IrF_{4} [T. Bzdusek et al., Nature 538, 75 (2016)], the nodal chain here is protected by mirror reflection symmetries of a simple space group, while in IrF_{4} the nonsymmorphic space group with a glide plane is a necessity. Moreover, in the presence of SOC, the nodal chain in WC-type HfC evolves into Weyl points. In the Brillouin zone, a total of 30 pairs of Weyl points in three types are obtained through the first-principles calculations. Besides, the surface states and the pattern of the surface Fermi arcs connecting these Weyl points are studied, which may be measured by future experiments.