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Three-dimensional topological semimetals are a class of electronic materials in which their bulk and surface states contain linear band touching nodes near the Fermi level. Like semiconductors, their properties will be affected by point and extended defects in their crystal structures, although the extent to which defects and disorders influence topological semimetals may differ in key ways due to their unique electronic structures. In this Tutorial, we provide an overview of the defects in topological semimetals, covering both computational and experimental methods for exploring defect-property relationships. We also include a discussion on open questions that still need to be explored further. [ABSTRACT FROM AUTHOR]

Solid-state thermomagnetic modules operating based on the Nernst–Ettingshausen effects are an alternative to conventional solid-state thermoelectric modules. These modules are appropriate for low-temperature applications where the thermoelectric modules are not efficient. Here, we briefly discuss the application, performance, similarities, and differences of thermoelectric and thermomagnetic materials and modules. We review thermomagnetic module design, Nernst coefficient measurement techniques, and theoretical advances, emphasizing the Nernst effect and factors influencing its response in semimetals such as carrier compensation, Fermi surface, mobility, phonon drag, and Berry curvature. The main objective is to summarize the materials design criteria to achieve high thermomagnetic performance to accelerate thermomagnetic materials discovery. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) transition metal dichalcogenides with 2H-phases, as a unique platform of valleytronics, display valley polarization and the well-known anomalous valley Hall effect when stacking with 2D magnetic substrates. In this study, we employ first-principles calculations to investigate the magnetic states, band structures, and magnetic proximity-dependent valley properties of 2D van der Waals heterostructures Cr2Ge2Te6/2H-MX2 (M = Mo, W, and X = S, Se, Te). Our findings reveal that the heterostructures possess stacking-dependent spontaneous valley polarization as well as pristine perpendicular magnetic anisotropy. Additionally, the Berry curvature and circular polarization demonstrate the presence of spin–momentum coupling characteristics, while the calculated non-zero Hall voltage indicates that the anomalous valley Hall effect can be achieved in valley-polarized systems. Furthermore, due to the strain effect and the electronic polarization at the interface, Cr2Ge2Te6/2H-MX2 heterostructures undergo the transition from semiconductors to semimetals upon substitution of early chalcogen elements. These calculations provide valuable insights for practical applications of valleytronics in 2D van der Waals heterostructure systems. [ABSTRACT FROM AUTHOR]

Transition metal catalysts supported on topological insulators are predicted to show improved catalytic properties due to the presence of topological surface states, which may float up to the catalysts and provide robust electron transfer. However, experimental studies of surface structures and corresponding catalytic properties of transition metal/topological insulator heterostructures have not been demonstrated so far. Here, we report the structures, chemical states, and adsorption behaviors of two conventional transition metal catalysts, Pt and Pd, on the surface of Bi2Se3, a common topological insulator material. We reveal that Pt forms nanoparticles on the Bi2Se3 surface. Moreover, the interaction between Pt and surface Se is observed. Furthermore, thermal dosing of O2 onto the Pt/Bi2Se3 heterostructure leads to no oxygen adsorption. Detailed scanning tunneling microscopy study indicates that Pt transforms into PtSe2 after the thermal process, thus preventing O2 from adsorption. For another transition metal Pd, it exhibits approximate layer-island growth on Bi2Se3, and Pd–Se interaction is also observed. Our work provides significant insights into the behaviors of transition metals on top of a common topological insulator material and will assist in the future design of catalysts built with topological materials. [ABSTRACT FROM AUTHOR]

The binary high-pressure phase diagram of the Ta–Sb system was constructed for the first time in this study, utilizing the evolutionary algorithm USPEX and density functional theory (DFT). Ten pressurized dynamically and mechanically stable or metastable novel phases of Ta–Sb were discovered, including I4/mmm-TaSb2, P4/nmm-TaSb, P-3-Ta2Sb7, I4/mmm-Ta2Sb3, P-4m2-Ta7Sb, Pm-3-Ta7Sb, Pmm2-Ta15Sb, P4/nmm-TaSb3, I4/mmm-Ta3Sb4, and I4/mmm-Ta2Sb5. The compounds P-4m2-Ta7Sb and Pmm2-Ta15Sb exhibit promising characteristics as non-centrosymmetric superconductors (NCSs), with their superconducting critical temperature (TC) being 3.831 and 3.221 K, respectively. The application of pressure tuning is predicted to transform the topological characteristics of P4/nmm-TaSb, causing it to transition from a topological insulator state to a Dirac semimetal state and ultimately reverting back to a topological insulator state. Therefore, the P4/nmm-TaSb compound is considered a promising candidate to investigate topological and superconducting excitations. Moreover, the mechanical and thermal properties of Ta–Sb binary phases were also investigated. The thermal conductivity of I4/mmm-TaSb2, P4/nmm-TaSb, and P4/nmm-TaSb3 all surpasses 20 W m−1 K−1 at 1000 K, showcasing their excellent thermal conductivity properties. The present study addresses the research gap concerning high-pressure structures in the Ta–Sb binary system, thereby offering valuable insights for the design and development of intermetallic compounds within this binary system. [ABSTRACT FROM AUTHOR]

Transition metal catalysts supported on topological insulators are predicted to show improved catalytic properties due to the presence of topological surface states, which may float up to the catalysts and provide robust electron transfer. However, experimental studies of surface structures and corresponding catalytic properties of transition metal/topological insulator heterostructures have not been demonstrated so far. Here, we report the structures, chemical states, and adsorption behaviors of two conventional transition metal catalysts, Pt and Pd, on the surface of Bi2Se3, a common topological insulator material. We reveal that Pt forms nanoparticles on the Bi2Se3 surface. Moreover, the interaction between Pt and surface Se is observed. Furthermore, thermal dosing of O2 onto the Pt/Bi2Se3 heterostructure leads to no oxygen adsorption. Detailed scanning tunneling microscopy study indicates that Pt transforms into PtSe2 after the thermal process, thus preventing O2 from adsorption. For another transition metal Pd, it exhibits approximate layer-island growth on Bi2Se3, and Pd–Se interaction is also observed. Our work provides significant insights into the behaviors of transition metals on top of a common topological insulator material and will assist in the future design of catalysts built with topological materials. [ABSTRACT FROM AUTHOR]

With the in-depth study of open optical systems, the topological phases of non-Hermitian metasurfaces have attracted increasing attention due to their topological protection properties. Here, in this paper, a tunable non-Hermitian metasurface with bidirectional anisotropism is proposed. By incorporating the phase change material vanadium dioxide (VO2) into the metasurface, two topological exceptional points (EPs) appear in the system by adjusting the conductivity of VO2 and chiral responses appear at both EPs. This research shows that the conductivity significantly affects the reflection of the metasurface, and the zero-reflection points correspond to the EPs of the non-Hermitian system. Further results prove that circling around EPs leads to a 2π phase change, which is topologically protected and independent of the encirclement path. Therefore, this study employs an active control approach to realize two topological EPs. Through comprehensive investigations into the topological properties and chiral performance at EPs, we elucidate the mechanism for the chirality generation in non-Hermitian metasurfaces, which offers feasible solutions for the development of chiral topological devices and light transmission and modulation in future applications. [ABSTRACT FROM AUTHOR]

MnBi2Te4 can generate a variety of exotic topological quantum states, which are closely related to its special structure. We conduct comprehensive multiple-cycle high-pressure research on MnBi2Te4 by using a diamond anvil cell to study its phase transition behaviors under high pressure. As observed, when the pressure does not exceed 15 GPa, the material undergoes an irreversible metal–semiconductor–metal transition, whereas when the pressure exceeds 17 GPa, the layered structure is damaged and becomes irreversibly amorphous due to the lattice distortion caused by compression, but it is not completely amorphous, which presents some nano-sized grains after decompression. Our investigation vividly reveals the phase transition behaviors of MnBi2Te4 under high pressure cycling and paves the experimental way to find topological phases under high pressure. [ABSTRACT FROM AUTHOR]

MnBi2Te4 can generate a variety of exotic topological quantum states, which are closely related to its special structure. We conduct comprehensive multiple-cycle high-pressure research on MnBi2Te4 by using a diamond anvil cell to study its phase transition behaviors under high pressure. As observed, when the pressure does not exceed 15 GPa, the material undergoes an irreversible metal–semiconductor–metal transition, whereas when the pressure exceeds 17 GPa, the layered structure is damaged and becomes irreversibly amorphous due to the lattice distortion caused by compression, but it is not completely amorphous, which presents some nano-sized grains after decompression. Our investigation vividly reveals the phase transition behaviors of MnBi2Te4 under high pressure cycling and paves the experimental way to find topological phases under high pressure. [ABSTRACT FROM AUTHOR]

Development of nanophotonics has made it possible to control the wavelength and direction of thermal radiation emission, but it is still limited by Kirchhoff's law. Magneto-optical materials or Weyl semimetals have been used in recent studies to break the time-reversal symmetry, resulting in a violation of Kirchhoff's law. Currently, most of the work relies on the traditional optical design basis and can only realize the nonreciprocal thermal radiation at a specific angle or wavelength. In this work, on the basis of material informatics, a design framework of a multilayer nonreciprocal thermal absorber with high absorptivity and low emissivity at any arbitrary wavelength and angle is proposed. Through a comprehensive investigation of the underlying mechanism, it has been discovered that the nonreciprocal thermal radiation effect is primarily attributed to excitation of the cavity mode at the interface between the metal and the multilayer structure. Moreover, the impact of factors, such as layer count, incidence angle, extinction coefficient, and applied magnetic field on nonreciprocal thermal radiation, is thoroughly explored, offering valuable insights to instruct the design process. Additionally, by expanding the optimization objective, it becomes feasible to design fixed dual-band or even multi-band nonreciprocal thermal absorbers. Consequently, this study offers essential guidelines for advancing the control of nonreciprocal thermal radiation. [ABSTRACT FROM AUTHOR]

In the present study, we have explored the absorption properties of a monolayer graphene-based photonic heterostructure, which consists of topological photonic configurations, graphene, and a Bragg mirror. The optical attributes were computed by using the 4 × 4 transfer matrix method. The results indicate that the creation of topological interface states and strong coupling between these resonant modes result in mode splitting, leading to the formation of hybrid modes known as coupled topological interface states with unity transmittance. The number of absorption modes can be modulated with an appropriate selection of cascaded photonic structures. Our proposed design with 1, 3, 5, and 7 cascaded topological photonic structures provides 1, 5, 9, and 13 absorption modes with greater than 90 % absorption. The findings also reveal that absorption peak strength is greatly influenced by Fermi-level and magnetic fields; switching of the modes from absorption to reflection and vice versa is achieved by suitable electrical and magnetic biasing. Our proposed design offers various applications, such as switchable filters, absorbers, and modulators. [ABSTRACT FROM AUTHOR]

Structural, electronic, magnetic and optical properties of Cu4Mn2Te4 have been reported earlier by the authors, and here, the transport properties of the same are discussed along with the band structure investigation of the neodymium-doped cubic material LMO (LiMn2O4), namely LiMn 1. 7 5 Nd 0. 2 5 O4 compound, under spin polarized schemes through the First Principles calculations. The Full Potential-Linearized Augumented Plane Wave Method (FP-LAPW) method is adopted to investigate the electronic structures based on the framework of Density Functional Theory (DFT). Exchange potentials are treated using the Generalized Gradient Approximations (GGA). Cohesive energy calculations reveal that the ferromagnetic phase of LiMn 1. 7 5 Nd 0. 2 5 O4 and the antiferromagnetic phase of Cu4Mn2Te4 exhibits a stable phase. Of these, FM-LiMn 1. 7 5 Nd 0. 2 5 O4 shows a semi-metallic-like behavior in spin-up channel and metallic behavior in spin-down channel whereas antiferromagnetic Cu4Mn2Te4 exhibits a band gap in both spin-up and spin-down channels. Dirac points are identified at −0.0625 eV in the band structure plot of FM-LiMn 1. 7 5 Nd 0. 2 5 O4 at its high symmetry points Γ and W which is an indication of high electron mobility at ambient condition. The presence of flat and dispersive bands around the Fermi energy level is an indication of high thermopower, and it is present in both the compounds FM-LiMn 1. 7 5 Nd 0. 2 5 O4 and AFM-Cu4Mn2Te4. From the present computations, at 300 K, a power factor range of ( S 2 σ scaled by relaxation time in μ W/msK2) 1. 7 5 × 1 0 2 0 ↑ and 9. 3 7 × 1 0 2 1 ↓ is obtained for ferromagnetic LiMn 1. 7 5 Nd 0. 2 5 O4 compounds at up and down spins, respectively. A typical power factor (μ Wm − 1 s − 1 K − 2 ) of 4. 7 9 × 1 0 1 5 ↑ and 2. 9 7 × 1 0 1 8 ↓ is obtained for antiferromagnetic Cu4Mn2Te4 at 325 K required for good thermoelectric performance. [ABSTRACT FROM AUTHOR]

Exposure to toxic metals and metalloids is a significant public health concern and can seriously affect human health. The aim of this study was to establish the presence of toxic metals and metalloids in the urine of non‐professional sportsmen who participated in a mountain ultramarathon using a benchtop total reflection x‐ray fluorescence (TXRF) system. TXRF allows for easy and rapid sample preparation and is therefore a potential candidate for simple and cost‐effective analysis. In this work, the TXRF‐Mo system was used for multielement analysis of the urine samples of 21 non‐professional athletes who ran a 53 km mountain ultra‐marathon. Urine samples were collected at four time points, at the beginning of the race (pre‐race samples), immediately, and 12 and 24 h post‐race. Al, As, Ba, Ni, Pb, Rb, Sr, V, and Tl were detected in the collected urine samples. The accuracy and precision of the proposed methods were verified by the analysis of reference materials (Seronorm™ Trace Elements Urine Level 2). The TXRF results were in agreement with the reference values and no significant differences were observed at the 95% confidence level. The detection limits for the elements of interest were also reasonable considering their concentration ranges in real samples. Changes were observed over time with increasing average urinary metals and metalloids levels, but only two significant results, were an increase in As and Rb. The results indicate a high degree of inter‐subject variability. The results obtained show that the content of toxic metals and metalloids increases in the urine samples collected after the race, which could confirm the statement that physical activity can increase the excretion of toxic metals and metalloids from the body. The simplicity of the TXRF method as well as its fast performance make it suitable for routine analysis. [ABSTRACT FROM AUTHOR]

Pulsed solid‐state lasers comprise 2D materials as saturable absorbers that contain transparent windows of the atmosphere and characteristic fingerprint spectra of several vital molecules that are significant in various applications and research. Over the past few decades, significant progress has been made in the development of narrow pulse width, high energy, high average output power, high efficiency, and simple construction of passively Q‐switched and mode‐locked lasers with 2D materials as saturable absorbers. This review summarizes the development of 2D materials, including graphene, transition metal dichalcogenides, black phosphorus, topological insulators, and MXenes, as modulator devices for solid‐state lasers owing to their broadband operation, excellent nonlinear optical response, low recovery time, ultrafast dynamic processing, and easy fabrication. Then, some new emerging and representative applications of pulsed solid‐state lasers are introduced and illustrated such as laser surgery, material processing, and lidar. Finally, future challenges and perspectives of pulsed solid‐state lasers with 2D materials‐based saturable absorbers are analyzed and addressed. The rapid development of pulsed solid‐state lasers with the continuous improvement of modulation technology is expected to expand opportunities for application in industry, scientific, medical, and other areas. [ABSTRACT FROM AUTHOR]

Bose metals are metals made of Cooper pairs, which form at very low temperatures in superconducting films and Josephson junction arrays as an intermediate phase between superconductivity and superinsulation. We predicted the existence of this 2D metallic phase of bosons in the mid 1990s, showing that they arise due to topological quantum effects. The observation of Bose metals in perfectly regular Josephson junction arrays fully confirms our prediction and rules out alternative models based on disorder. Here, we review the basic mechanism leading to Bose metals. The key points are that the relevant vortices in granular superconductors are core-less, mobile XY vortices which can tunnel through the system due to quantum phase slips, that there is no charge-phase commutation relation preventing such vortices from being simultaneously out of condensate with charges, and that out-of-condensate charges and vortices are subject to topological mutual statistics interactions, a quantum effect that dominates at low temperatures. These repulsive mutual statistics interactions are sufficient to increase the energy of the Cooper pairs and lift them out of condensate. The result is a topological ground state in which charge conduction along edges and vortex movement across them organize themselves so as to generate the observed metallic saturation at low temperatures. This state is known today as a bosonic topological insulator. [ABSTRACT FROM AUTHOR]

The production and consumption of coffee generates large amounts of waste which, if released into the environment, could cause unacceptable pollution. The search for alternatives for the use of these waste materials, namely coffee silver skin (CSS) and spent coffee grounds (SCG), is of great importance from an environmental and economic point of view. In this context, the present study was conducted to evaluate the use of CSS and SCG as mineral sources in order to strengthen their status as novel foods, which is currently not recognised. With the aim of validating the content of metals and metalloids in CSS and SCG, a comparative study of green and roasted coffee was also conducted. The results of the HR-ICP-MS analyses showed that coffee and coffee by-products contain high levels of macro essential elements: K (2387–35 993 mg/kg), Mg (1263–5298 mg/kg) and Na (82.6–170 mg/kg). Among the essential trace elements, Fe predominated with amounts between 41.8 and 728 mg/kg. The essential elements in the ultra-trace range (Mo, Cr, Co and Se) are found in amounts between 0.02 and 2.42 mg/kg. The content of toxic elements (Pb, As, Cd and Sn) is in the range of 0.01–0.25 mg/kg, which is below the maximum levels set by the EU Commission for these elements in foodstuff. However, the levels of Rb, Ba, Sr, Ti and Al are high, and range from 2.33 to 764 mg/kg. Considering the high content of essential elements in CSSs that are useful for daily human needs, the potential use of CSS should be encouraged. On the other hand, in order to meet the requirements for the use of novel foods, monitoring of potentially toxic elements must be carried out. [ABSTRACT FROM AUTHOR]

Purpose: The radionuclides pollution base on MMs (metals and metalloids) near uranium mines has been drawing broad attention, but the extent of their impact on soil and human health is still unclear. Therefore, the aim of this study was to investigate the distribution and health risk assessments of 238U, 226Ra, 232Th and 40 K base on MMs (Cr, Ni, Cu, Zn, As, Cd, and Pb) in different surface soils near an uranium mine. Materials and methods: Surface soil samples were extracted from 35 representative sites near the Lefu uranium mine. Radionuclides and MMs were measured using high-purity germanium (HPGe) N-type coaxial detector and inductively coupled plasma mass spectrometer, respectively. Pollution status was evaluated using DR, Raeq, AEDE, Hext, and ELCR for radionuclides and Pi, Igeo, RI and health risk index for MMs. Their correlation was analyzed through Pearson/Spearman correlation analysis. Results and discussion: The average activity concentration of 238U, 226Ra, 232Th, and 40 K are 504, 1227, 118, and 769 Bq·kg−1 respectively and the average concentration of Cr, Ni, Cu, Zn, As, Cd, and Pb are 200, 33.9, 41.3, 132, 18.4, 0.26, and 78.7 mg·kg−1, respectively. Values of DR, Raeq, AEDE, Hext, and ELCR all exceed the world average to varying degrees and values of Pi, Igeo, RI and the health risk index are within the acceptable ranges. Correlation analyses showed that 238U, 226Ra, 232Th and Pb are strongly correlated (correlation coefficient > 0.6) with each other. Conclusions: On the basis of the obtained values, it can be concluded that generally higher radionuclides and MMs were distributed near the Lefu uranium. There are potential health risks associated with the elevated radioactivity. The overall situation of MMs is controllable, however, particular attention is warranted for Cr and Cd, as they approach values-at-risk. The strong correlations between 238U, 226Ra, 232Th and Pb imply a uniform pollution level or a possible shared source. [ABSTRACT FROM AUTHOR]

HgTe has been considered to be one of the most versatile topological materials. Depending on the in‐plane strain, Weyl and Dirac semi‐metal, as well as topological insulator phases, are feasible. Here, for the first time it is reported, that an InAs:S substrate promotes an initial 2D growth of a ZnTe thin layer and subsequent high crystalline quality ZnTe/CdTe superlattices serve as a smooth and continuous virtual substrate for the growth of (Cd,Hg)Te/HgTe/(Cd,Hg)Te heterostructures with unstrained quantum well HgTe (topological insulator) and compressively strained bulk HgTe (Weyl semimetal) by molecular beam epitaxy. Compared with the superlattices previously grown on GaAs substrates, the quantum well and bulk heterostructures exhibit homogeneous surfaces with root mean square roughnesses of 0.88–0.93 nm, which is three times lower than those observed for 3D islands (2.7–3.4 nm) on GaAs substrates. Additionally, magnetotransport measurements confirm high electronic quality and demonstrate that the S‐doped InAs substrate can be used as an effective back gate. These results manifest a (big) step forward toward the improvement of micro‐ and nanometer‐sized top‐ and back‐gated device fabrication on topological materials. [ABSTRACT FROM AUTHOR]

Layered ternary type‐II Weyl semimetals demonstrate promising applications in high‐performance and broadband optoelectronics, therefore it is crucial to gain insights into their photocarriers’ dynamics. In this work, the probing polarization dependence of non‐equilibrium dynamics in NbIrTe4 is investigated by using transient reflectivity spectroscopy. Following photoexcitation at 3.18 eV, the dynamical response of 1.59 eV probe pulse exhibits a strong dependence on probe polarization. The relaxation comprises two components: a rapid recovery of ≈0.6 ps attributed to the electron–phonon scattering, and an anomalous slow recovery spanning hundreds of picoseconds attributed to the photoinduced quasi‐particle. The polarization dependence of rapid relaxation time τ is indicative of the in‐plane anisotropy of electron–phonon coupling in NbIrTe4. The slow relaxation modulated by a latest reported 16 cm−1 coherent phonon also shows strong probing polarization dependence, further revealing the anisotropic nature of electron–phonon coupling and the possibility of anisotropic lattice distortion, as well as photoinduced polaron, under ultrafast photoexcitation in NbIrTe4. The dynamical anisotropy in NbIrTe4 has provided valuable guidance for the application of NbIrTe4 in polarization‐sensitive nonlinear optics or optoelectronic devices and offers insights into the unique carrier transport as well as phonon transport properties of this newly established topological material. [ABSTRACT FROM AUTHOR]

High theoretical capacity, stabilized and layered 2H phase molybdenum disulfide (2H) is regarded as a promising material for superior kinetics anode in sodium ion battery, but the inherent semiconducting properties and sluggish sodium ions diffusion limit the development of 2H based anode. Hence, this study builds a unique metalloid phase with high electronic conductivity and suitable layer structure by screening non‐metallic carbon atoms doped in 2H (2H‐C). As experimental and simulation results, 2H‐C of metalloid properties after carbon atom modulation exhibit superior sodium storage kinetics and reversibility by a unique mechanism that promotes ion intercalation under high voltage window, and further good for the later uniformly conversion at lower voltage (intercalation‐conversion mechanism). The 2H‐C anode material delivers a remarkable reversible capacity of 156 mAh g−1 at ultra‐high 100.0 A g−1, long‐term life of 6000 cycles, and superior performance at low temperatures of −10 °C. Otherwise, 2H‐C/Na3V2(PO4)3 full cell also performs charge/discharge capacity of 80.0/76.7 mAh g−1 with 87% capacity retention after 140 cycles at 0 °C. This discovery further explores the unique mechanism and application of 2D layered materials in sodium‐ion battery anodes for fast kinetics under extreme conditions. [ABSTRACT FROM AUTHOR]

Specific properties, such as surface Fermi arcs, features of quantum oscillations and of various responses to a magnetic field, distinguish Dirac semimetals from ordinary materials. These properties are determined by Dirac points at which a contact of two electron-energy bands occurs and in the vicinity of which these bands disperse linearly in the quasimomentum. This work shows that almost the same properties are inherent in a wider class of materials in which the Dirac spectrum can have a noticeable gap comparable with the Fermi energy. In other words, the degeneracy of the bands at the point and their linear dispersion are not necessary for the existence of these properties. The only sufficient condition is the following: In the vicinity of such a quasi-Dirac point, the two close bands are well described by a two-band model that takes into account the strong spin-orbit interaction. To illustrate the results, the spectrum of ZrTe5 is considered. This spectrum contains a special quasi-Dirac point, similar to that in bismuth. Dirac semimetals are 3D materials where the conduction and valence bands meet at what are called Dirac points. The author shows that almost all the properties inherent in the Dirac semimetals are exhibited by a wider class of materials that need not have the gapless Dirac points. [ABSTRACT FROM AUTHOR]

The chiral magnetic effect (CME) is a collective quantum phenomenon that arises from the interplay between gauge field topology and fermion chiral anomaly, encompassing a wide range of physical systems from semimetals to quark-gluon plasma. This paper, with a focus on CME and related effects in heavy ion collisions, aims to provide an introductory discussion on its conceptual foundation and measurement methodology, a timely update on the present status in terms of experimental findings and theoretical progress, as well as an outlook into the open problems and future developments. [ABSTRACT FROM AUTHOR]

Topological materials are currently considered excellent catalysts for heterogeneous processes because of their surface metallic states and excellent carrier mobility. This work will show that cubic palladium bronze LaPd3S4 is an ideal topological material with multifold fermions, Fermi arcs on the (001) surface, and high catalytic performance for electrochemical hydrogen evolution reactions (HER). A direct correlation has been discovered between the position of the multifold fermions (related to the Fermi level) and Gibbs free energy (ΔGH*). Moreover, by applying the vertical electric field and uniaxial strain to the LaPd3S4, the multifold fermions disappear, and the |ΔGH*| increases, weakening the HER activity. This correlation establishes a clear connection between increased catalytic performance and topological states and fully elucidates the underlying process in topological catalysis. [ABSTRACT FROM AUTHOR]

Herein, via first‐principle calculations and theoretical analysis, a new Dirac semimetal carbon system called C32, which is composed of pentagonal, hexagonal, heptagonal, and octagonal carbon rings is systematically investigated. The stability of C32 is verified by calculating the phonon dispersion, elastic constants, etc., and an appropriate pathway for experimental synthesis is proposed. Besides, it is discovered that the system holds the quadruple rotation and inversion symmetry, resulting in the emergence of eight twisted Dirac cones (D1 and D2) with a highly anisotropic Fermi velocity from 3.83 × 105 to 8.96 × 105 m s−1 along different k directions. To substantiate the semimetallic nature of C32, its nontrivial topological properties are confirmed through the presence of topologically protected edge states, and the nonzero ℤ2 topological invariant. More importantly, by introducing biaxial strain, it is uncovered that Dirac cones can gradually evolve into a nodal line, and the perfect nodal line can be obtained when the biaxial strain is 13.3%. Furthermore, by constructing the tight‐binding model, the appearance of the Dirac cone is perfectly repeated and its evolution into the nodal line under biaxial strain is explained. [ABSTRACT FROM AUTHOR]

In this review, the thermoelectric properties in nodal‐point semimetals with two bands are discussed. For the two‐dimensional (2D) cases, it is shown that the expressions of the thermoelectric coefficients take different values depending on the nature of the scattering mechanism responsible for transport, by considering examples of short‐ranged disorder potential and screened charged impurities. An anisotropy in the energy dispersion spectrum invariably affects the thermopower quite significantly, as illustrated by the results for a node of semi‐Dirac semimetal and a single valley of graphene. The scenario when a magnetic field of magnitude B$B$ is applied perpendicular to the plane of the 2D semimetal is also considered. The computations for the three‐dimensional (3D) cases necessarily involve the inclusion of nontrivial Berry phase effects. In addition to demonstrating the expressions for the response tensors, the exotic behavior observed in planar Hall and planar thermal Hall set‐ups is discussed. [ABSTRACT FROM AUTHOR]

The investigations of polar topological conformations have become one of the hotspots due to their multitudinous physical properties and potential applications in emerging electronic devices. However, constructing polar topologies in bulk form is exceedingly challenging. In this study, bubble domains with different polar topologies, including flux-closure and half-closure, are successfully achieved in Cu-doped (K,Na)(Nb,Ta)O 3 single crystals by elaborately adjusting the phase structure and defect dipoles. The coexistence of orthorhombic and tetragonal phases results in a flattened free energy landscape, while the presence of a high concentration of defect dipoles in local regions leads to the generation of the strong internal electric field, further modifying the energy profile. The interplay of various types of energies gives rise to the smooth rotation of the polar vectors, facilitating the formation of topological structures. These findings provide a practical method for constructing topological bubble domains in bulk materials, thereby enriching the understanding of the physical properties arising from topological structures. [ABSTRACT FROM AUTHOR]

Topological materials are currently considered excellent catalysts for heterogeneous processes because of their surface metallic states and excellent carrier mobility. This work will show that cubic palladium bronze LaPd3S4 is an ideal topological material with multifold fermions, Fermi arcs on the (001) surface, and high catalytic performance for electrochemical hydrogen evolution reactions (HER). A direct correlation has been discovered between the position of the multifold fermions (related to the Fermi level) and Gibbs free energy (ΔGH*). Moreover, by applying the vertical electric field and uniaxial strain to the LaPd3S4, the multifold fermions disappear, and the |ΔGH*| increases, weakening the HER activity. This correlation establishes a clear connection between increased catalytic performance and topological states and fully elucidates the underlying process in topological catalysis. [ABSTRACT FROM AUTHOR]

Low-dimensional materials with topologically protected edge states have wide applications in spintronic, valleytronic, and optoelectronic nanodevices. Different from the valley-resolved quantum anomalous Hall (VQAH) state and spin-polarized quantum anomalous Hall (VSQAH), the photon-induced topological states in kagome-lattice nanoribbons (KLNR) can generate both valley and spin-polarized edge states without magnetic substrate or Rashba spin-orbit coupling (SOC). Via the Floquet theory, we also propose a 0-photon-extraction scheme to obtain the effective Hamiltonian under low-frequency light for the first time, and we analyze the topological properties and phase transition of the irradiated kagome system, similar with those in the high-frequency case. We then design an all-optically controlled valley-resolved spin filter based on KLNR. Transmissions and local current distributions of the proposed nanodevice confirm this spin-filter effect, which can indeed be switched by left- or right-circularly-polarized (LCP/RCP) light. We believe these optically controlled models can be extended to the design of magnetism-free spin-valley filter or switcher in the future. [ABSTRACT FROM AUTHOR]

The 8 × 8 magneto-optical matrix has been derived to discuss the Faraday rotation (FR) effect, which is induced by the linear polarization wave passing through a sandwich structure composed of a dielectric layer and two identical Weyl semimetals (WSMs). The giant enhanced FR angle about 45° can be realized at the resonant tunneling wavelength of right hand circularly polarization (RCP) waves by enlarging the difference of the resonant tunneling wavelength of RCP and left hand circularly polarization waves suitably. It is shown that the resonant wavelengths depend on the Weyl node separation and tilt degree of Weyl cones in both type-I and type-II WSMs. More importantly, there exists a tunable one-to-one relationship between the Weyl node separation and the wavelength of the resonant FR angle, as well as the tilt degree and the wavelength of the resonant FR angle, which enables the characteristic of the Weyl node separation and tilt degree. Our research reveals an available method to determine the Weyl node separation and tilt degree of Weyl cones in both type-I and type-II WSMs. [ABSTRACT FROM AUTHOR]

We study the evolution of band topology under external pressure in rare-earth gadolinium mono-antimonide (GdSb) using first-principles calculations. This material crystallizes in a rocksalt-type structure and shows a structural phase transition (SPT) to a CsCl-type structure at 26.1 GPa. The phonon dispersions are analyzed to ascertain the dynamical stability of this material. We use hybrid density functional theory with the inclusion of spin–orbit coupling to investigate the structural, electronic, and topological phase transitions (TPTs). At ambient pressure, GdSb shows a topologically trivial state which is in agreement with existing experimental reports. The first TPT is observed at 6 GPa of hydrostatic pressure (at the high symmetry X -point) which is verified with the help of single-band inversion and surface state analysis along the (001) plane. The non-zero value of the first Z2 topological invariant and the presence of the Dirac cone also confirm the topological phase of this material. A further increase in pressure to 12 GPa results in two band inversions at Γ - as well as X - points, which corresponds to the trivial nature of GdSb. The same is also verified with (0; 000) values of Z2 topological invariants and a pair of Dirac cones in surface states. It is noted that the crystal symmetries are preserved throughout the study and the TPT values are much lower than the SPT pressure, i.e. 26.1 GPa. [ABSTRACT FROM AUTHOR]

In recent years, the skyrmion lattice phase with a short lattice constant has attracted attention due to its high skyrmion density, making it a promising option for achieving high-density storage memory and for observing novel phenomena like the quantized topological Hall effect. Unlike conventional non-centrosymmetric systems where the Dzyaloshinsky–Moriya interaction plays a crucial role, the short pitch skyrmion phase requires a quadratic magnetic interaction J (q) with a peak at finite- Q , and weak easy-axis magnetic anisotropy is also critical. Thus, conducting first-principles evaluations is essential for understanding the formation mechanism as well as for promoting the discovery of new skyrmion materials. In this Perspective, we focus on recent developments of the first-principles evaluations of these properties and apply them to the prototype systems Gd T 2 X 2 and Eu T 2 X 2 , where T denotes a transition metal and X represents Si or Ge. In particular, based on the spin density functional theory with the Hubbard correction combined with the Liechtenstein method in the Wannier tight-binding model formalism, we first show that the Hubbard U and Hund's coupling is essential to stabilize a skyrmion lattice state by enhancing the easy-axis anisotropy. We then discuss mechanisms of finite- Q instability and show that competition among Gd-5 d orbitals determines whether ferromagnetism or a finite- Q structure is favored in Gd T 2 Si 2 with T = Fe and Ru. Our systematic calculations reveal that GdRu 2 X 2 , GdOs 2 X 2 , and GdRe 2 X 2 are promising, while GdAg 2 X 2 , GdAu 2 X 2 , and EuAg 2 X 2 are possible candidates as the skyrmion host materials. Analysis based on a spin spiral calculation for the candidate materials is also presented. [ABSTRACT FROM AUTHOR]

We have investigated magnetic interactions between transition metal ions in bismuthene topological insulators with protected edge states. We find that these topological states have a crucial role in the magnetic interactions in 2D topological insulators. Using first-principles and model Hamiltonian, we make a comparative study of transition metal doped bulk and nanoribbon bismuthene. While a direct overlap between the transition metal prevails in gapped bulk bismuthene, at the borders of nanoribbons, a long-range magnetism is present. The exchange interactions are well described by a Ruderman–Kittel–Kasuya–Yosida-like Hamiltonian mediated by massive and topological states. Our results show a dominance of antiferromagnetism promoted by the topological states, preserving the spin-locked Dirac crossing states due to a global time-reversal symmetry preservation. This extended magnetic interactions mediated mainly by massless electrons can increase the spin diffusion length being promising for fast dissipationless spintronic devices. [ABSTRACT FROM AUTHOR]

Trace metals and metalloids are groups of chemical elements that naturally occur in low concentrations and cycle in the environment driven by natural processes and human activities. They have a persistent and bio-accumulative tendency in the environment, and certain trace metals and metalloids have become a public health concern. This study assesses the concentration of eleven trace metals and a metalloid in sediments and catfish muscle from five study sites in the Eastern Tanzanian River basin. Forty catfish tissues and fifteen sediment samples were collected and analyzed using ICP-MS. Concentrations of As, Cd, Co, Pb, and Zn did not exceed the United States Environmental Protection Agency (USEPA) guideline for pollution of sediments, while Al Cr, Al, Mn, and V with values ranging from (118.54 to 70154.55) indicating moderately polluted. The stations Java-Sadaani and Matandu showed the highest Cr, Ni, and Cu concentrations, but the potential ecological risk index (RI) was low (RI < 95). In the catfish muscle tissue, the levels of Cd, Pb, Cu, and Zn did not surpass the EU and FAO/WHO limits and results ranged from 2.22 to 35.22mg/kg. Low levels of accumulation of Cd, Pb, and As were found in this study compared to catfish muscles from other studies, whereas the concentrations of other trace metals and metalloids analyzed had comparable results. Biota/sediment accumulation factors (BSAF) were all < 1. The weekly metal intake (MWI) results ranged from 6.89E-04 to 2.43E+01 μg/know-1week-1, indicating a low risk as the value did not exceed the FAO/WHO established Permissible Tolerable Weekly Intake (PTWI). The non-carcinogenic health risk result THQ was 4.43E-02 and the carcinogenic health risks result HI was 4.42E-05 which indicated tolerable levels of risks as both the values of the Target Hazard Quotient (THQ) and the Hazard Index (HI) was < 1, and the carcinogenic target risk (TR) is < 0.0001. The highest TR values were observed for Cr and Ni. We recommend a continued monitoring of the changes in trace metal levels in the environment and biota together with continuous public health education on the dangers of high levels of trace metals. [ABSTRACT FROM AUTHOR]

The estrogen receptor alpha (ERa) plays a central role in the etiology, progression, and treatment of breast cancers. Constitutively activating somatic mutations Y537S and D538G, in the ligand binding domain (LBD) of ESR1, are associated with acquired resistance to endocrine therapies. We have previously shown that the metalloestrogen calcium activates ERa through an interaction with the LBD of the receptor. This study shows that cadmium activates ERa through a mechanism similar to calcium and contributes to, and further increases, the constitutive activity of the ERa mutants Y537S and D538G. Mutational analysis identified C381, N532A, H516A/N519A/E523A, and E542/ D545A on the solvent accessible surface of the LBD as possible calcium/metal interaction sites. In contrast to estradiol, which did not increase the activity of the Y537S and D538G mutants, cadmium increased the activity of the constitutive mutants. Mutation of the calcium/metal interaction sites in Y537S and D538G mutants resulted in a significant decrease in constitutive activity and cadmium induced activity. Mutation of calcium/metal interaction sites in wtERa diminished binding of the receptor to the enhancer of estrogen responsive genes and the binding of nuclear receptor coactivator 1 and RNA polymerase II. In contrast to wtERa, mutation of the calcium/metal interaction sites in the Y537S and D538G mutants did not diminish binding to DNA but prevented a stable interaction with the coactivator and polymerase. Growth assays further revealed that calcium channel blockers and chelators significantly decreased the growth of MCF7 cells expressing these constitutively active mutants. Taken together, the results suggest that exposure to cadmium plays a role in the etiology, progression, and response to treatment of breast cancer due, in part, to its ability to activate ERa. [ABSTRACT FROM AUTHOR]

Heusler compounds belong to a large family of materials and exhibit numerous physical phenomena with promising applications, particularly ferromagnetic Weyl semimetals for their use in spintronics and memory devices. Here, anomalous Hall transport is reported in the room‐temperature ferromagnets NiMnSb (half‐metal with a Curie temperature (TC) of 660 K) and PtMnSb (pseudo half‐metal with a TC of 560 K). They exhibit 4 µB/f.u. magnetic moments and non‐trivial topological states. Moreover, NiMnSb and PtMnSb are the first half‐Heusler ferromagnets to be reported as Weyl semimetals, and they exhibit anomalous Hall conductivity (AHC) due to the extended tail of the Berry curvature in these systems. The experimentally measured AHC values at 2 K are 1.8 × 102 Ω−1 cm−1 for NiMnSb and 2.2 × 103 Ω−1 cm−1 for PtMnSb. The comparatively large value between them can be explained in terms of the spin‐orbit coupling strength. The combined approach of using ab initio calculations and a simple model shows that the Weyl nodes located far from the Fermi energy act as the driving mechanism for the intrinsic AHC. This contribution of topological features at higher energies can be generalized. [ABSTRACT FROM AUTHOR]

The recent discovery of anti‐chiral edge states in magnetic semimetals linking two unequal‐frequency bulk Dirac nodes manifests a paradoxical picture in contrast to the chiral behavior in Chern insulators, implying an untapped phase may exist. Here, a unique Chern metal, exhibiting a nontrivial Chern number but without a complete bandgap is proposed, and the complete topological phase diagram in the modified Haldane model is obtained. Subsequently, the Chern metal in a 2D honeycomb‐lattice gyromagnetic photonic crystal by simultaneously breaking parity and time‐reversal symmetries with opposite and unequal magnetic biases at different sublattices is realized. For the paired complementary‐shape boundaries, such as zigzag/bearded, it is experimentally revealed that either clockwise or counter‐clockwise chiral character is switchable in Chern metals relying on different boundary choices, a remarkable property deemed as bi‐chiral edge propagation. The topological Chern metal with hidden bulk‐boundary correspondence is articulated to bridge the chiral and anti‐chiral paradox gap between Chern insulators and magnetic semimetals. These results enrich the family of Chern materials and highlight the previously untapped on‐demand control of topological edge states. [ABSTRACT FROM AUTHOR]

Light-rare-earth-based RAlSi family serves as an exceptional platform for elucidating the unique properties of Weyl systems, featuring both types of Weyl fermions, with and without magnetism. In this investigation, we conducted a comparative analysis of the resistivity and magnetoresistance (MR) behaviors of single-crystal RAlSi (R = La, Ce, and Pr). A hump appears in the temperature-dependent resistivity curve of CeAlSi, attributed to the crystal-electric-field effect and showing insensitivity to the magnetic field. In nonmagnetic LaAlSi, a quasilinear MR response above the crossover field is linked to mobility fluctuations originating from slight inhomogeneity. Upon heating CeAlSi from 2 K to its critical temperature for ferromagnetic (FM) ordering (TC), a field-induced contraction in the twin Fermi surfaces was observed, likely contributing to negative MR peaks at TC. The robustness of Weyl nodes in FM RAlSi is demonstrated by the inherent broken space inversion symmetry, allowing them to change positions via violation of time-reversal symmetry. Our findings suggest the potential for magnetic modulation of the electronic structure in FM RAlSi, leading not only to shifts in Weyl nodes but also alterations in the Fermi surface. [ABSTRACT FROM AUTHOR]

Radionuclides and heavy metals/metalloids content in soils and shore sediments of Al-Negila area (Matrouh, Egypt) were determined to assess the associated environmental risks. A total of 46 soil and shore sediment samples were collected and analysed for natural and man-made radionuclides (238U series, 232Th series, 40K and 137Cs) and heavy metals/metalloids (Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mn, Ni, Si, Sr, Zn, and Hg). Within the study area, the soil and shore sediments are mainly calcareous with sandy, sandy clay and silty clay sized textures. The radionuclides and metals/metalloids concentrations in the soil were higher than those in the shore sediments, meanwhile, they are within the safe world average values. The estimated average (±SD) activity concentrations of 226Ra, 228Ra, 40K and 137Cs were 20.3 ± 5.3, 17.8 ± 6.3, 353.1 ± 129.8, and 2.7 ± 2.7 Bq/kg, respectively. The activity concentration of 137Cs is characterised by the greatest variability characterising the fallout deposited radionuclides. The estimated average values of Raeq (72.9 ± 23.7 Bq/kg), air absorbed gamma dose rate (34.9 ± 11.4 nGy/h), annual effective dose (42.8 ± 14.0 µSv/y), and external hazard index (0.2 ± 0.1) are lower than the international averages reported by UNSCEAR 2008. The average concentrations (mg/kg) of heavy metals/metalloids in soil samples decrease in the following order: Mn (129.8) > Sr (95.0) > Si (28.8) > Ba (25.7) > Zn (25.1) > Cr (17.6) > B (10.0) > Ni (3.9) > Cu (3.3) > Co (0.5) > Cd (0.007) > Hg (7.0 µg/kg). According to the classes of pollution load and contamination degree indices, soils and shore sediments of Al-Negila area are generally uncontaminated. However, a few sampling sites were considered moderately contaminated with B, Cd, and Sr. The radionuclides and heavy metal/metalloid contents in the soil and shore sediments of the area should be observed and assessed regularly, especially for 137Cs. [ABSTRACT FROM AUTHOR]

Two-dimensional topological semimetals are typically characterized by the vorticity of gapless points, and can be classified according to the band representations. However, the topological properties involving the distribution of the Berry curvature in the entire Brillouin zone are often overlooked. In this study, we investigate a two-band two-dimensional topological semimetal protected by C4zT magnetic symmetry, exhibiting a two-fold band degeneracy at the Γ(0, 0) and M(π, π) points. Due to the presence of C4zT symmetry, the Brillouin zone is divided into two patches characterized by half-quantized Berry curvature fluxes with opposite signs. In multi-band case, the half-quantization deviates, indicating the fragile nature. The semimetal presents counter-propagating half-edge channels, accompanied by power-law decaying and oscillating edge currents. The band topology leads to unconventional Landau levels featuring anisotropic edge modes. Each massless Dirac cone, associated with the half-quantized Berry curvature flux, exhibits an integer quantum Hall conductance. Additionally, we calculate the local orbital magnetization with open boundary conditions in both the x and y directions. This reveals isolated magnetization islands, highlighting an experimentally observable magnetic phenomenon in this topological semimetal. A two-dimensional semimetal is featured by its low energy physics near the degeneracy points, while the topology over the whole Brillouin zone is rarely studied. The authors find that the Brillouin zone of the C4zT symmetric semimetal is partitioned into two patches characterized by half quantized Berry curvature fluxes with opposite signs, accompanied by the topological transport phenomena. [ABSTRACT FROM AUTHOR]

Kondo physics has long been interesting for studying correlated topology in isolation, as it occurs in heavy fermion compounds where myriad phenomena are well-separated in energy. We introduce magnetic topological Kondo semimetal phases of matter into the literature in this work to advance the understanding of correlated topological semimetal physics by studying a layered three-dimensional heterostructure in which two types of Kondo insulators are stacked alternatingly. In the heterostructures considered, one of these Kondo insulators is SmB6, a potential topological Kondo insulator, and the other one is an isostructural Kondo insulator AB6, where A is a rare-earth element, e.g., Eu, Yb, or Ce. We find that if the latter Kondo insulator orders ferromagnetically, the heterostructure generically becomes a magnetic Weyl Kondo semimetal, while antiferromagnetic order can yield a magnetic Dirac Kondo semimetal. We also confirm the realization of the magnetic Weyl (Dirac) Kondo semimetal phase in density functional theory calculations of the heterostructure of SmB6 and EuB6 (CeB6). Our results demonstrate that Kondo insulator heterostructures are a versatile platform for realizing correlated topological semimetal phases. [ABSTRACT FROM AUTHOR]

Edge states of a topological insulator can be used to explore fundamental science emerging at the interface of low dimensionality and topology. Achieving a robust conductance quantization, however, has proven challenging for helical edge states. In this work, we show wide resistance plateaus in kink states—a manifestation of the quantum valley Hall effect in Bernal bilayer graphene—quantized to the predicted value at zero magnetic field. The plateau resistance has a very weak temperature dependence up to 50 kelvin and is flat within a dc bias window of tens of millivolts. We demonstrate the electrical operation of a topology-controlled switch with an on/off ratio of 200. These results demonstrate the robustness and tunability of the kink states and its promise in constructing electron quantum optics devices. [ABSTRACT FROM AUTHOR]

Topological materials usually possess protected gapless states in either the boundary or bulk, exhibiting various properties such as spin-momentum locking, Klein tunneling, Fermi arcs and so on. Database searches using symmetry data at high-symmetry points have catalogued thousands of topological materials revealing a magnitude of band nodes (BNs) at high-symmetry points or lying within high-symmetry lines/planes. A complete mapping from symmetry data (namely, representation of little group) in any BN to the k ⋅ p model characterizing low-energy Hamiltonian around the BN (and from the k ⋅ p model to concrete BN, inversely), is expected to complete the characterization of all BNs and gapless states. Here we first review recent progress on classifying BNs by systematically and automatically constructing k ⋅ p models based on recently completed tabulation of all irreducible (co-)representation matrices of little groups of the 1651 magnetic space groups. As one indispensable input in constructing a symmetry-allowed and generic k ⋅ p model, the expansion order, has been carefully and systematically truncated for any BN to a reasonable nonzero integer, by comparing the emanating nodal structure (ENS, including nodal point, nodal line and nodal surface) near the BN obtained by the explicitly constructed k ⋅ p model and that by pure symmetry analysis using compatibility relations (CRs). Owing to the progress, we are able to summarize all 25 different configurations of ENS near BN required by CRs, provide a complete mapping from k ⋅ p model to its realization around BN, and the corresponding ENS by CRs in an accessible file, and also reveal the protection mechanism of additional nodal lines that escape conventional analysis by CRs and is only predictable by constructing k ⋅ p model. The symmetry-based classification results on all BNs could facilitate large-scale materials prediction and hold promise for realizing topological semimetals suitable for device applications. [ABSTRACT FROM AUTHOR]

The article discusses a new protocol for quantum secure direct communication (DI-QSDC) using hyper-entanglement, which ensures secure communication despite device imperfections. The protocol increases the capacity of the secure channel by utilizing hyper-encoding. The article also mentions the AAPPS-DACG Workshop, an international symposium on cosmology and particle astrophysics, and highlights the achievements of Chinese physicist Qi-Kun Xue. Xue has made significant contributions to condensed matter physics, particularly in the study of the quantum anomalous Hall effect (QAHE), and his work has led to advancements in understanding and applying quantum Hall states. Xue has received recognition and prestigious prizes for his achievements in the field of physics. [Extracted from the article]

Ultra‐broadband photodetectors based on semimetal crystals have recently become popular because of their gapless band structures. In particular, semimetal crystals have large carrier mobility or high Seebeck coefficient; this almost eliminates the possibility of using semimetal crystals as photodetectors. In addition, a larger temperature gradient can cause photocurrent generation based on the photothermoelectric effect. Surprisingly, the TaTe2 crystal has a huge absorption coefficient (≈104 cm−1), a minimal specific heat (≈0.172 J g−1 K−1), and a low thermal conductivity (0.3 W m−1 K−1), which is beneficial for generating a high photothermal conversion efficiency of 30.2%, despite its small Seebeck coefficient, and achieving a large temperature gradient occurs for the heat generated by external illumination. Herein, the possibility of photoresponse based on the TaTe2 detector is explored, which has a low carrier mobility (≈10 cm2 V−1 s−1) and a small Seebeck coefficient (≈7.1 µV K−1). The self‐powered TaTe2 photodetector can also provide a competitive photoresponse range from 355 to 2715 nm and exhibit a maximum responsivity of 1.1 mA W−1 with a detectivity of 4.7 × 108 Jones at 455 nm. This study provides a new design scheme and operating mechanism for semimetal photodetectors and enriches semimetal crystal photodetectors. [ABSTRACT FROM AUTHOR]

Platinum-based intermetallic compounds (IMCs) play a vital role as electrocatalysts in a range of energy and environmental technologies, such as proton exchange membrane fuel cells. However, the synthesis of IMCs necessitates recombination of ordered Pt-M metallic bonds with high temperature driving, which is generally accompanied by side effects for catalysts' structure and performance. In this work, we highlight that semimetal atoms can trigger covalent interactions to break the synthesis-temperature limitation of platinum-based intermetallic compounds and benefit fuel-cell electrocatalysis. Attributed to partial fillings of p-block in semimetal elements, the strong covalent interaction of d-p π backbonding can benefit the recombination of ordered Pt-M metallic bonds (PtGe, PtSb and PtTe) in the synthesis process. Moreover, this covalent interaction in metallic states can further promote both electron transport and orbital fillings of active sites in fuel cells. The semimetal-Pt IMCs were obtained with a temperature 300 K lower than that needed for the synthesis of metal-Pt intermetallic compounds and reached the highest CO-tolerant oxygen reduction activity (0.794 A mg−1 at 0.9 V and 5.1% decay under CO poisoning) among reported electrocatalysts. We anticipate that semimetal-Pt IMCs will offer new insights for the rational design of advanced electrocatalysts for fuel cells. [ABSTRACT FROM AUTHOR]

The non-reciprocal behavior of defect modes of a one-dimensional photonic crystal with two Weyl-semimetal-based defects is investigate by applying the transfer matrix method. The transmission spectrum of the structure exhibits two distinct defect modes. The study shows that these defect modes can be adjusted by altering the thickness of the Weyl semimetal layers and the modulus of the axial vector $ \vec{b} $ b → for both forward- and backward-impinging cases. The peak transmission and frequency of the defect modes are found to be dependent on the thickness of the Weyl semimetal layers, the magnitude of the axial vector $ \vec{b} $ b → , and the impinging direction of the incoming beam. Additionally, the quality factor of the defect modes changes with the thickness of the Weyl semimetal layers and the magnitude of the axial vector $ \vec{b} $ b → but is largely unaffected by reversing the impinging direction of the incoming beam. [ABSTRACT FROM AUTHOR]

As the most prevalent element on our planet, carbon manifests a wide variety of allotropic phases, significantly contributing to its complex physical properties. Recently, several carbon allotropes have been reported to possess abundant topological phases in theory and experiment. This work focuses on a sp3 carbon allotrope, Z-ACA allotrope, which consists of 5-6-7-type Z-ACA carbon rings. This allotrope has been reported previously as a superhard material comparable to diamond. In this study, we report that it is a candidate for both an obstructed atomic insulator and a real Chern insulator. It is worth mentioning that Z-ACA exhibits an unconventional bulk-boundary correspondence due to its hinge boundary state manifestation. Our current research indicates that Z-ACA is a suitable carbon phase platform for studying the real topology and second-order bulk-boundary correspondence. [ABSTRACT FROM AUTHOR]

Metal contamination in drinking water is well known; however, detailed insights into the metals/metalloids in finished water and their health effects are lacking. Water samples collected over four seasons from August 2022 to April 2023 from three locations in the Yangtze River basin in Nanjing were analyzed using inductively coupled plasma mass spectrometry to detect 33 metal/metalloid types. This study assessed seasonal and spatial variations and evaluated the removal efficiencies of advanced treatment processes. Health risks from metal/metalloid ingestion were calculated using a risk assessment model from the United States Environmental Protection Agency (USEPA). No significant regional differences in total metal/metalloid concentrations were found between the source and finished waters. Metals such as Cr, Ga, Hg, Pb, and Rb varied seasonally, peaking in winter. The advanced treatment process outperformed the conventional process for As removal. However, the removal efficiencies were lower for Mn, Cd, Hg, Se, and Zn than those of the conventional process. Positive correlations were observed among several metals, suggesting that metals may have similar sources of contamination. The main carcinogenic risk exceeded the acceptable levels in children according to the USEPA. Non-carcinogenic risks were below the threshold values, but As, Tl, and V were highlighted as key risk elements. Seasonal changes markedly influenced metal/metalloid concentrations and distributions in water, necessitating risk management focused on arsenic. [ABSTRACT FROM AUTHOR]

The manipulation of solid states using intense infrared or terahertz light fields is a pivotal area in contemporary ultrafast photonics research. While conventional circular polarization has been well explored, the potential of counterrotating bicircular light remains widely underexplored, despite growing interest in theory. In the mid-infrared or multi-terahertz region, experimental challenges lie in difficulties in stabilizing the relative phase between two-color lights and the lack of available polarization elements. Here, we successfully generated phase-stable counterrotating bicircular light pulses in the 14–39 THz frequency range circumventing the above problems. Employing spectral broadening, polarization pulse shaping with a spatial light modulator, and intra-pulse difference frequency generation leveraging a distinctive angular-momentum selection rule within the nonlinear crystal, we achieved direct conversion from near-infrared pulses into the designed counterrotating bicircular multi-terahertz pulses. Use of the spatial light modulator enables programmable control over the shape, orientation, rotational symmetry, and helicity of the bicircular light field trajectory. This advancement provides a novel pathway for the programmable manipulation of light fields, and marks a significant step toward understanding and harnessing the impact of tailored light fields on matter, particularly in the context of topological semimetals. Phase-stable counterrotating bicircular light pulses, including a trefoil-like field trajectory, were realized in multi-terahertz range. Orientation, shape, rotational symmetry, and helicity of trajectories are programmable on software. [ABSTRACT FROM AUTHOR]