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The valley-polarized quantum anomalous Hall (VP-QAH) materials, which combine valley polarization and the quantum anomalous Hall (QAH) effect, are of both fundamental and technological importance due to their potential applications for nanoscale devices. Here, we explored the stability, magnetic, and topological properties of two-dimensional MnTiX2 (X = F/Cl/Br) monolayers based on first-principles calculations. Our results show that all the structures have robust antiferromagnetic orders with large magnetic anisotropic energies and high transition temperatures (480–670 K). In the absence of spin–orbital coupling (SOC), the MnTiX2 monolayers represent antiferromagnetic quadratic crossing semimetals. In the presence of SOC, the quadratic crossing points of the systems are opened with sizable bandgaps (> 0.5 eV), and they are transformed to be QAH insulators with |C| = 1. Moreover, the MnTiF2 monolayer is found to be a spontaneous VP-QAH semiconductor due to the time reversal symmetry and inversion symmetry being broken. These insights provide an ideal platform for achieving VP-QAH materials for dissipationless transport and quantum computing. [ABSTRACT FROM AUTHOR]

[Display omitted] Owing to the outstanding properties provided by nontrivial band topology, topological phases of matter are considered as a promising platform towards low-dissipation electronics, efficient spin-charge conversion, and topological quantum computation. Achieving ferroelectricity in topological materials enables the non-volatile control of the quantum states, which could greatly facilitate topological electronic research. However, ferroelectricity is generally incompatible with systems featuring metallicity due to the screening effect of free carriers. In this study, we report the observation of memristive switching based on the ferroelectric surface state of a topological semimetal (TaSe 4) 2 I. We find that the surface state of (TaSe 4) 2 I presents out-of-plane ferroelectric polarization due to surface reconstruction. With the combination of ferroelectric surface and charge-density-wave-gapped bulk states, an electric-switchable barrier height can be achieved in (TaSe 4) 2 I-metal contact. By employing a multi-terminal-grounding design, we manage to construct a prototype ferroelectric memristor based on (TaSe 4) 2 I with on/off ratio up to 103, endurance over 103 cycles, and good retention characteristics. The origin of the ferroelectric surface state is further investigated by first-principles calculations, which reveal an interplay between ferroelectricity and band topology. The emergence of ferroelectricity in (TaSe 4) 2 I not only demonstrates it as a rare but essential case of ferroelectric topological materials, but also opens new routes towards the implementation of topological materials in functional electronic devices. [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) Weyl semimetal, akin to a spinful variant of graphene, represents a topological matter characterized by Weyl fermion-like quasiparticles in low dimensions. The spinful linear band structure in two dimensions gives rise to distinctive topological properties, accompanied by the emergence of Fermi string edge states. We report the experimental realization of a 2D Weyl semimetal, bismuthene monolayer grown on SnS(Se) substrates. Using spin and angle-resolved photoemission and scanning tunneling spectroscopies, we directly observe spin-polarized Weyl cones, Weyl nodes, and Fermi strings, providing consistent evidence of their inherent topological characteristics. Our work opens the door for the experimental study of Weyl fermions in low-dimensional materials. 2D Weyl semimetals are spin-polarized analogues of graphene that promise access to various topological properties of matter. Here, the authors evidence spin-polarized Weyl cones, Weyl nodes, and Fermi strings in monolayer bismuthene. [ABSTRACT FROM AUTHOR]

Topological invariants are crucial quantities for classifying materials with topological phases. Hence, their connections with experimentally measurable quantities are extremely important. In this context, circular dichroism (CD) provides a protocol to detect the Chern number 0 of the lowest energy Bloch band (LBB) of a semimetal. This hinges on the unequal depletion rates of the Bloch electrons from a filled LBB, under the action of a time-periodic circular drive, depending on the chirality of the polarization. According to the dimensionality of the system (i.e., whether it is two- or three-dimensional), the integrated differential rate for depletion has to be formulated a bit differently in order to relate it to 0 . Our aim is to capture the nature of the CD response for semimetals with anisotropic band dispersions. We show that while the quantization of the CD response for the three-dimensional cases is strongly sensitive to anisotropy, the two-dimensional counterparts show a perfectly quantized response. [ABSTRACT FROM AUTHOR]

Nanoporous graphene (NPG) materials are generated by removing internal degree-3 vertices from graphene and introducing nanopores with specific topological structures, which have been widely explored and exploited for applications in electronic devices, membranes, and energy storage. The inherent properties of NPGs, such as the band structures, field effect mobilities and topological properties, are crucially determined by the geometric structure of nanopores. On-surface synthesis is an emerging strategy to fabricate low-dimensional carbon nanostructures with atomic precision. In this review, we introduce the progress of on-surface synthesis of atomically precise NPGs, and classify NPGs from the aspects of element types, topological structures, pore shapes, and synthesis strategies. We aim to provide a comprehensive overview of the recent advancements, promoting interdisciplinary collaboration to further advance the synthesis and applications of NPGs. On-surface synthesis is a useful approach for the construction of nanoporous graphene materials, which are in turn of interest for various electronic applications. Here, the authors review the latest developments in the on-surface synthesis of atomically precise pristine and hetero-atom doped nanoporous graphene materials. [ABSTRACT FROM AUTHOR]

The bulk photovoltaic effect (BPVE) in non-centrosymmetric materials has attracted significant attention in recent years due to its potential to surpass the Shockley-Queisser limit. Although these materials are strictly constrained by symmetry, progress has been made in artificially reducing symmetry to stimulate BPVE in wider systems. However, the complexity of these techniques has hindered their practical implementation. In this study, we demonstrate a large intrinsic photocurrent response in centrosymmetric topological insulator Ag2Te, attributed to the surface photogalvanic effect (SPGE), which is induced by symmetry reduction of the surface. Through diverse spatially-resolved measurements on specially designed devices, we directly observe that SPGE in Ag2Te arises from the difference between two opposite photocurrent flows generated from the top and bottom surfaces. Acting as an efficient SPGE material, Ag2Te demonstrates robust performance across a wide spectral range from visible to mid-infrared, making it promising for applications in solar cells and mid-infrared detectors. More importantly, SPGE generated on low-symmetric surfaces can potentially be found in various systems, thereby inspiring a broader range of choices for photovoltaic materials. The bulk photovoltaic effect holds promise for various optoelectronic applications, but it is usually restricted to non-centrosymmetric materials operating in the visible range. Here, the authors report a surface photogalvanic effect spanning from visible to midinfrared wavelengths in a centrosymmetric topological insulator, Ag2Te. [ABSTRACT FROM AUTHOR]

Contamination by metals poses a significant threat to marine ecosystems and the health of marine organisms, including cetaceans. This study aimed to assess the concentrations of some metal and metalloids in the skin of bottlenose dolphins (Tursiops truncatus) from the Yucatan Peninsula in Mexico using Flame Atomic Absorption (FAA) spectrometry. A total of 41 skin samples were collected, comprising 22 samples from Yucatán in the Gulf of Mexico and 19 samples from Chetumal Bay in the Caribbean. The results of our analysis revealed the presence of various elements in the skin of bottlenose dolphins from coastal waters in the Yucatan Peninsula. Among the detected metals, zinc (Zn), iron (Fe), and arsenic (As) exhibited notable concentrations, with the order of abundance being Zn > Fe > As > Cu > Cr > Cd > Ni. The elevated concentrations of Zn and Fe suggest potential exposure and accumulation of these metals in the studied dolphin population. Interestingly, measurable concentrations of lead (Pb) and manganese (Mn) were not detected in the skin samples, indicating either low levels or the absence of their accumulation in the studied dolphin populations. The absence of measurable Pb concentrations is particularly encouraging as Pb is known to have detrimental effects on marine organisms and is commonly associated with anthropogenic activities. This study provides valuable insights into the metal contamination status in bottlenose dolphins from the Yucatan Peninsula, Mexico. The notable concentrations of Zn, Fe, and As raise concerns about potential health risks to these charismatic marine mammals. Further research is warranted to investigate the sources and pathways of heavy metal exposure in this population and to understand the potential consequences of such exposure on the health and well-being of bottlenose dolphins in the Yucatan Peninsula. [ABSTRACT FROM AUTHOR]

In graphene on transition metal dichalcogenides, two types of spin–orbit coupling (SOC)—Rashba and spin–valley Zeeman SOCs—can coexist that modify graphene's electronic band differently. Herein, it is shown that the Landau levels (LLs) are also affected by these SOCs distinctively enough to estimate their relative strengths from the Landau fan diagram. A simple theoretical model is used to calculate the LL spectra of graphene for different SOC strengths, revealing that when the total SOC is strong enough (i.e., when it is comparable to the half of the energy gap between the LLs of an intrinsic graphene), the corresponding LLs will split and cross with others depending sensitively on the relative strengths of the SOC terms. To demonstrate how one can use it to estimate the relative SOC strengths, the four key features that are well separated from the complex background are first identified and compared with experiment to show that in the sample investigated, the Rashba SOC is stronger than the spin–valley Zeeman SOC consistent with other spectroscopic measurements. The study therefore provides a simple and practical strategy to analyze the LL spectrum in graphene with SOC before carrying out more in‐depth measurements. [ABSTRACT FROM AUTHOR]

Heavy metal and metalloid pollution in reservoir systems has attracted widespread attention due to their toxic, persistent, and nonbiodegradable characteristics. This study investigated the distribution and risks of heavy metals and metalloids in the sediment and drawdown area of the Fengshuba reservoir system. Sediment phase exhibited substantial heavy metal and metalloid pollution and higher ecological risk that the drawdown phase. There were significant differences in the structure and composition of the total metal content and the bioavailable fraction between the sediment and the drawdown area, which indicates that the total metal content and the bioavailable fraction might dominantly regulate by a complex combination of sediment characteristics. Positive Matrix Factorization model was used to identify sources of heavy metals and metalloids pollution and revealed that heavy metals and metalloids contamination in Fengshuba reservoir might originate from anthropogenic activities. Evaluations from risk assessment show that As and Cd in the reservoir system may pose health risks. Knowledge of distribution, potential risk assessment, and source apportionment of heavy metals and metalloids in the Fengshuba drinking water is critical in promoting the sustainable development of the reservoir, developing water management and conservation strategies in the Fengshuba reservoir. [ABSTRACT FROM AUTHOR]

Decades ago, Gurzhi proposed that if momentum-conserving collisions prevail among heat-carrying phonons in insulators and charge-carrying electrons in metals, hydrodynamic features will become detectable. In this paper, we will review the experimental evidence emerging in the last few years supporting this viewpoint and raising new questions. The focus of the paper will be bulk crystals without (or with a very dilute concentration of) mobile electrons and steady-state thermal transport. We also discuss the possible link between this field of investigation and other phenomena, such as the hybridization of phonon modes and the phonon thermal Hall effect. [ABSTRACT FROM AUTHOR]

The presented study suggests a silicon photonic topological insulator with triple Dirac points, each associated with a specific valley; there is a contrast in the chirality (handedness) of the photon states between these valleys. This contrasting chirality results in interesting optical properties, potentially leading to topologically protected robust wave guiding effect in compact structure with sharp edge. [ABSTRACT FROM AUTHOR]

We report interfacial transport properties in in situ grown orthorhombic perovskite oxide heterostructures consisting of an antiferromagnetic insulator DyFeO3 and a paramagnetic conductor CaRuO3. We observe Hall effect with a step-like increase amounting to an effective magnetic field of 30 T at 20 K. We provide a plausible explanation in the context of topological Hall effect originating from a non-coplanar spin texture and resultant emergent field in DyFeO3 associated with the scalar spin chirality. Our results demonstrate that the proximity effect of the emergent field at heterointerfaces is a universal physical phenomenon, while it has been reported originally in a heterointerface composed of pyrochlore oxides. This will greatly expand the choice of materials to the heterointerfaces for the research in emergent transport phenomena, which has been limited to single compounds with both metallic properties and special spin textures. Additionally, this will pave the way for possible device application of the emergent field by designing and combining perovskite oxides with versatile functionalities such as multiferroicity. [ABSTRACT FROM AUTHOR]

The emerging field of photonic topological insulators offers promising platforms for high-performance optical communication, computing, and sensing. However, conventional photonic topological insulator designs typically operate within the diffraction limit due to their dielectric nature. This limitation imposes constraints on device miniaturization, reduces light–matter interaction, and decreases overall device sensitivity. Introducing a new valley-Hall hybrid plasmonic topological insulator, we overcome this limitation by exploiting the coupling of surface plasmon oscillations with the optical modes of a dielectric photonic crystal, allowing for sub-diffraction vertical confinement of light. Deep-subwavelength chiral edge states can, therefore, be generated and robustly guided along disordered Z-shaped topological boundaries with much lower propagation loss compared to purely plasmonic platforms. Such extreme manipulation of light on an integrated chip platform maximizes light–matter interaction and opens the door for truly compact and efficient optical modulators, molecular sensors, and next-generation nanophotonic and quantum devices. [ABSTRACT FROM AUTHOR]

The USEPA issued the "Framework for Metal Risk Assessment" in 2007, recognizing that human and environmental exposure to metals and metalloids (MMEs) poses challenges risk assessment. Inhalation of aerosols containing MMEs is a primary pathway for exposure in the occupational setting, for consumer exposure, and to general population exposure associated with point‐source emissions or ambient sources. The impacts of inhalation can be at the point of deposition (local exposure) or may manifest after uptake into the body (systemic exposure). Both local and systemic exposure can vary with factors that determine the regional deposition of MME‐containing aerosols. Aerosol characteristics such as particle size combine with species‐specific characteristics of airway morphology and lung function to modulate the deposition and clearance of MME particulates. In contrast to oral exposure, often monitored by measuring MME levels in blood or urine, inhalation exposure can produce local pulmonary impacts in the absence of significant systemic distribution. Exposure assessment for nutritionally essential MMEs can be further complicated by homeostatic controls that regulate systemic MME levels. Predictions of local exposure can be facilitated by computer models that estimate regional patterns of aerosol deposition, permitting calculation of exposure intensity in different regions of the respiratory tract. The utility of deposition modeling has been demonstrated in assessments of nutritionally essential MMEs regulated by homeostatic controls and in the comparison of results from inhalation studies in experimental animals. This facilitates extrapolation from animal data to humans and comparisons of exposures possessing mechanistic linkages to pulmonary toxicity and carcinogenesis. Pulmonary deposition models have significantly advanced and have been applied by USEPA in evaluations of particulate matter. However, regional deposition modeling has yet to be incorporated into the general guidance offered by the agency for evaluating inhalation exposure. Integr Environ Assess Manag 2024;20:952–964. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Key Points: The USEPA is urged to promote the application of models for regional deposition in assessing impacts of inhalation exposure to metal and metalloid particulate matter.The local and systemic impacts of inhaled metals and metalloids are determined by patterns of regional deposition in the respiratory tract. [ABSTRACT FROM AUTHOR]

In the present study, first-principles molecular dynamics simulations were employed to study the effects of small amounts of B and C substituted for P on the structure and magnetic properties of Fe80P13C7, Fe80P10C7B3, and Fe80P8C9B3 amorphous alloys. A small amount of B and C replacing P atoms increases the icosahedral structure of the amorphous alloys, especially the increase in the regular icosahedral structure. The saturation magnetization of the three kinds of amorphous alloys gradually increases with the addition of B and C atoms, and the results of experimental and simulated calculations show consistent trends. The substitution of P atoms by B and C atoms leads to the aggregation of Fe atoms, which increases the magnetic moment of the iron atoms. In addition, the improvement of local structural symmetry may be one of the reasons for the increase in saturation magnetization of amorphous alloys. The substitution of a small number of B and C atoms plays an important role in improving the saturation magnetization of the amorphous alloy, which has a certain guiding significance for the development of amorphous alloys with excellent soft magnetic properties. [ABSTRACT FROM AUTHOR]

Both biochars (BCs) and modified-biochars (MBCs) for toxic-metal/metalloid ions (TMIs) removal from water have caught much attention owing to their exceptional properties such as eco-friendly, low-carbon emission and cost-effective. However, reviews on the exploration of theoretical models of BCs and MBCs in various systems are unobtainable. To give a summary of theoretical models on BCs and MBCs for TMIs removal in various solution systems, this review will center on some typical kinetic and isotherm equations of BCs and MBCs for TMIs sorption in a single, mixed, mixed metal ions/organic substance solutions. Typically, two-parameter and threeparameter kinetic and isotherm equations of BCs and MBCs for TMIs sorption were stressed. The comparisons of these models in various solution systems were drawn. It was found that P-2nd-O kinetic model, Langmuir and Freundlich isotherm models are the dominating adsorption manners for TMIs in various MSSs. Especially, only the kinetic models of Cu(II), Pb(II), Cr(VI) and Cd(II) sorption, as well as the isotherms of Cu(II) and Cd(II) sorption on BCs and MBCs were reported in these MSSs. We hope such a summary will be favorable for the accurately selecting of optimal models to explain the sorption processes in different metal-solution systems. [ABSTRACT FROM AUTHOR]

Increased anthropogenic activities are suspected to have contributed to the Tano basin heavy metal/metalloids water quality. However, data on land use contribution to the basin's heavy metal/metalloids pollution are limited. The study assessed the contribution of land use to the basin's heavy metals/metalloids pollution by assessing the levels of heavy metals/metalloids in 36 water samples taken from the source/control and experimental sites along the basin. Atomic absorption spectrophotometer was used to analysis samples. Metals/metalloids concentrations in water samples from the basin's source and the physicochemical parameters were compared with the corresponding concentrations in samples from the experimental sites. Significantly, higher heavy metal/metalloids concentrations and physicochemical levels were identified in the experimental sites than the source/control site. Heavy metal/metalloids levels at the source were as follows: As (0.001 ± 0.11 mg/L) < Cd (0.003 ± 0.34 mg/L) < Zn (0.011 ± 0.97 mg/L) but Pb, Hg, and Cr were not detected. The corresponding levels in the experimental sites were As (0.014 ± 0.88 mg/L) < Hg (0.051 ± 0.76 mg/L) < Cd (0.056 ± 0.45 mg/L) < Zn (0.166 ± 1.95 mg/L) < Cr (0.299 ± 0.42 mg/L) < Pb (0.428 ± 0.44 mg/L). Control water pH was slightly acidic (5.38 ± 3.4) but the experimental sites were near neutrality (7.35 ± 2.1). Noncarcinogenic and carcinogenic risks were detected for water consumption by children and adults in the experimental but none in the control. Land use activities identified were industrial, agricultural, and commercial. Enforcement of buffer zone protection laws is recommended. [ABSTRACT FROM AUTHOR]

Topological insulators generally have dielectric bulk and conductive surface states. Consequently, some of these materials are shown to support polaritonic modes at visible and THz frequencies. At the same time, the optical properties of topological insulators in the mid‐infrared (mid‐IR) remain poorly investigated. Here, near‐field imaging is employed to probe the mid‐IR response from the exfoliated flakes of bismuth (Bi)/selenide (Se)/telluride (Te)/antimony (Sb) crystals with varying stoichiometry – Bi2Se3, Bi2Te2Se, and Bi1.5Sb0.5Te1.7Se1.3 – in pristine form as well as covered by thin flakes of hexagonal boron nitride (hBN) is employed. Contrary to theoretical expectations, all three materials exhibit a dielectric response with a high refractive index and with a loss below the experimental detection limit. Particularly, the near‐field mapping of propagating phonon‐polaritons in hBN demonstrates that all three van der Waals crystals with different stoichiometry act as a practically lossless dielectric substrate with an ultra‐high refractive index of up to 7.5 in Bi2Te2Se. Such a unique dielectric crystal will be of great advantage for numerous nanophotonic applications in the mid‐IR. [ABSTRACT FROM AUTHOR]

In contrast to two-dimensional (2D) monolayer materials, van der Waals layered transition metal dichalcogenides exhibit rich polymorphism, making them promising candidates for novel superconductor, topological insulators and electrochemical catalysts. Here, we highlight the role of hydrostatic pressure on the evolution of electronic and crystal structures of layered ZrS2. Under deviatoric stress, our electrical experiments demonstrate a semiconductor-to-metal transition above 30.2 GPa, while quasi-hydrostatic compression postponed the metallization to 38.9 GPa. Both X-ray diffraction and Raman results reveal structural phase transitions different from those under hydrostatic pressure. Under deviatoric stress, ZrS2 rearranges the original ZrS6 octahedra into ZrS8 cuboids at 5.5 GPa, in which the unique cuboids coordination of Zr atoms is thermodynamically metastable. The structure collapses to a partially disordered phase at 17.4 GPa. These complex phase transitions present the importance of deviatoric stress on the highly tunable electronic properties of ZrS2 with possible implications for optoelectronic devices. Transition metal dichalcogenides exhibit rich polymorphism, making them promising candidates for superconductors, topological insulators, and electrochemical catalysts. Here, the authors study the metallization of non-hydrostatically compressed ZrS2 up to 45.8 GPa and find that a new high-pressure phase forms under deviatoric stress. [ABSTRACT FROM AUTHOR]

Plasmon polaritons, or plasmons, are coupled oscillations of electrons and electromagnetic fields that can confine the latter into deeply subwavelength scales, enabling novel polaritonic devices. While plasmons have been extensively studied in normal metals or semimetals, they remain largely unexplored in correlated materials. In this paper, we report infrared (IR) nano-imaging of thin flakes of CsV3Sb5, a prototypical layered Kagome metal. We observe propagating plasmon waves in real-space with wavelengths tunable by the flake thickness. From their frequency-momentum dispersion, we infer the out-of-plane dielectric function ϵ c that is generally difficult to obtain in conventional far-field optics, and elucidate signatures of electronic correlations when compared to density functional theory (DFT). We propose correlation effects might have switched the real part of ϵ c from negative to positive values over a wide range of middle-IR frequencies, transforming the surface plasmons into hyperbolic bulk plasmons, and have dramatically suppressed their dissipation. Plasmons polaritons, or collective excitations of electrons and electromagnetic fields, have been rarely studied in layered correlated materials. Shiravi et al. report hyperbolic plasmon polaritons in thin flakes of the Kagome metal CsV3Sb5 and discuss correlation effects on their formation and tunability. [ABSTRACT FROM AUTHOR]

Background: Major depressive disorder (MDD) pathogenesis may involve metalloids in a significant way. The aim of our study was to identify potential links between MDD and metalloid elements [boron (B), germanium (Ge), arsenic (As), antimony (Sb)]. Methods: A total of 72 MDD cases and 75 healthy controls (HCs) were recruited from Zhumadian Second People's Hospital in Henan Province, China. The levels of four metallic elements (B, Ge, As, and Sb) in the serum and urine were measured using inductively coupled plasma mass spectrometry (ICP-MS). Results: In comparison to the HCs, the B, As, and Sb levels were considerably lower in the MDD group (p < 0.05) in the serum; the MDD group had significantly higher (p < 0.05) and significantly lower (p < 0.001) B and Sb levels in the urine. After adjusting for potential confounders, serum B (OR = 0.120; 95% CI, 0.048, 0.300; p < 0.001) and Sb (OR = 0.133; 95% CI, 0.055, 0.322; p < 0.001) showed a negative correlation with MDD. Urine B had a negative correlation (OR = 0.393; 95% CI, 0.193, 0.801; p = 0.01) with MDD, while urine Sb had a positive correlation (OR = 3.335; 95% CI, 1.654, 6.726; p = 0.001) with MDD. Conclusion: Our current research offers insightful hints for future investigation into the function of metalloids in connection to MDD processes. [ABSTRACT FROM AUTHOR]

In this study, we discuss for the first time the relationships between the diversity of the bacterial population and of the metals and metalloids concentrations in the sediments of the Red River Delta, Vietnam. The analysis of the 16S rRNA by the Illumina technology revealed a diversified population and a potential of bioremediation by the microorganisms, notably by the Bacilli relatively abundant in the Bach Dang estuary, where high metals and metalloids concentrations were highlighted. This work offers new information on the environmental context of the delta and highlights the potential impact that metals and metalloids may have on the bacterial population. Further investigations on the role of the bacteria in the biogeochemistry of this ecosystem will be of interest for the development of bioremediation processes. [ABSTRACT FROM AUTHOR]

Dinuclear phosphinidene complexes bridging two transition metal centres are now well established. However, a phosphinidene bridging a metal centre and a main group Lewis acid has not yet been reported. Herein, we describe the generation of a highly reactive phosphinidene complex bridging a tungsten and a boron centre. Furthermore, the synthesis and dyotropic rearrangement of a P-borane adduct of an N-methylimidazole-stabilized neutral, electrophilic terminal phosphinidene complex is reported. [ABSTRACT FROM AUTHOR]

Flat electronic bands are expected to show proportionally enhanced electron correlations, which may generate a plethora of novel quantum phases and unusual low-energy excitations. They are increasingly being pursued in d-electron-based systems with crystalline lattices that feature destructive electronic interference, where they are often topological. Such flat bands, though, are generically located far away from the Fermi energy, which limits their capacity to partake in the low-energy physics. Here we show that electron correlations produce emergent flat bands that are pinned to the Fermi energy. We demonstrate this effect within a Hubbard model, in the regime described by Wannier orbitals where an effective Kondo description arises through orbital-selective Mott correlations. Moreover, the correlation effect cooperates with symmetry constraints to produce a topological Kondo semimetal. Our results motivate a novel design principle for Weyl Kondo semimetals in a new setting, viz. d-electron-based materials on suitable crystal lattices, and uncover interconnections among seemingly disparate systems that may inspire fresh understandings and realizations of correlated topological effects in quantum materials and beyond. Flat electronic bands can give rise to correlation-driven phases but for this, they need to be tuned to the Fermi level. Here the authors predict flat bands pinned at the Fermi level due to orbital-selective interactions and discuss implications for the design of topological Kondo semimetal in d-electron systems. [ABSTRACT FROM AUTHOR]

Transition metal compounds with kagome structure have been found to exhibit a variety of exotic structural, electronic, and magnetic orders. These orders are competing with energies very close to each other, resulting in complex phase transitions. Some of the phases are easily observable, such as the charge density wave (CDW) and the superconducting phase, while others are more challenging to identify and characterize. Here we present magneto-transport evidence of a new phase below ~ 35 K in the kagome topological metal CsV3Sb5 (CVS) thin flakes between the CDW and the superconducting transition temperatures. This phase is characterized by six-fold rotational symmetry in the in-plane magnetoresistance (MR) and is connected to the orbital current order in CVS. Furthermore, the phase is characterized by a large in-plane negative magnetoresistance, which suggests the existence of a three-dimensional, magnetic field-tunable orbital current ordered phase. Our results highlight the potential of magneto-transport to reveal the interactions between exotic quantum states of matter and to uncover the symmetry of such hidden phases. Recent studies reported evidence of a new phase in the kagome metal CsV3Sb5 between the charge density wave and superconducting transitions. Here the authors reveal symmetry properties of this phase in CsV3Sb5 thin flakes probed by in-plane magnetotransport, suggesting a 3D orbital current order. [ABSTRACT FROM AUTHOR]

The ability to finely tune the properties of magnetic topological insulators (TIs) is crucial for quantum electronics. We studied solid solutions with a general formula GexMn1-xBi2Te4 between two isostructural Z2 TIs, magnetic MnBi2Te4 and nonmagnetic GeBi2Te4 with Z2 invariants of 1;000 and 1;001, respectively. We observed linear x-dependent magnetic properties, composition-independent pairwise exchange interactions, and topological phase transitions (TPTs) between topologically nontrivial phases and the semimetal state. The TPTs are driven purely by the variation of orbital contributions. By tracing the x-dependent Bi 6p contribution to the states near the fundamental gap, the effective spin-orbit coupling variation is extracted. The gapless state observed at x = 0.42 closely resembles a Dirac semimetal above the Néel temperature and shows a magnetic gap below, which is clearly visible in raw photoemission data. The observed behavior demonstrates an ability to precisely control topological and magnetic properties of TIs. Topological insulators with ordered moments of embedded magnetic atoms are viable platforms for quantum electronics, but the practical applications are restricted by the size of their crystals. The authors synthesize a Z2 topological insulator GexMn1-xBi2Te4 in the form of a large crystal with high structural perfection and tunable magnetic and electronic properties. [ABSTRACT FROM AUTHOR]

Mining activities, even in arctic regions, create waste materials releasing metals and metalloids, which have an impact on the microorganisms inhabiting their surroundings. Some species can persist in these areas through tolerance to meta(loid)s via, e.g., metabolic transformations. Due to the interaction between microorganisms and meta(loid)s, interest in the investigation of microbial communities and their possible applications (like bioremediation or biomining) has increased. The main goal of the present study was to identify, isolate, and characterize microorganisms, from subarctic mine sites, tolerant to the metalloid antimony (Sb) and the metal copper (Cu). During both summer and winter, samples were collected from Finnish mine sites (site A and B, tailings, and site C, a water-treatment peatland) and environmental parameters were assessed. Microorganisms tolerant to Sb and Cu were successfully enriched under low temperatures (4°C), creating conditions that promoted the growth of aerobic and fermenting metal(loid) tolerating or anaerobic metal(loid) respiring organism. Microbial communities from the environment and Sb/Cu-enriched microorganisms were studied via 16S rRNA amplicon sequencing. Site C had the highest number of taxa and for all sites, an expected loss of biodiversity occurred when enriching the samples, with genera like Prauserella, Pseudomonas or Clostridium increasing their relative abundances and others like Corynebacterium or Kocuria reducing in relative abundance. From enrichments, 65 putative Sb- and Cu-metabolizing microorganisms were isolated, showing growth at 0.1 mM to 10 mM concentrations and 0°C to 40°C temperatures. 16S rRNA gene sequencing of the isolates indicated that most of the putative anaerobically Sbrespiring tolerators were related to the genus Clostridium. This study represents the first isolation, to our knowledge, of putative Sb-metabolizing cold-tolerant microorganisms and contributes to the understanding of metal (loid)-tolerant microbial communities in Arctic mine sites. [ABSTRACT FROM AUTHOR]

The ability to finely tune the properties of magnetic topological insulators (TIs) is crucial for quantum electronics. We studied solid solutions with a general formula GexMn1-xBi2Te4 between two isostructural Z2 TIs, magnetic MnBi2Te4 and nonmagnetic GeBi2Te4 with Z2 invariants of 1;000 and 1;001, respectively. We observed linear x-dependent magnetic properties, composition-independent pairwise exchange interactions, and topological phase transitions (TPTs) between topologically nontrivial phases and the semimetal state. The TPTs are driven purely by the variation of orbital contributions. By tracing the x-dependent Bi 6p contribution to the states near the fundamental gap, the effective spin-orbit coupling variation is extracted. The gapless state observed at x = 0.42 closely resembles a Dirac semimetal above the Néel temperature and shows a magnetic gap below, which is clearly visible in raw photoemission data. The observed behavior demonstrates an ability to precisely control topological and magnetic properties of TIs. Topological insulators with ordered moments of embedded magnetic atoms are viable platforms for quantum electronics, but the practical applications are restricted by the size of their crystals. The authors synthesize a Z2 topological insulator GexMn1-xBi2Te4 in the form of a large crystal with high structural perfection and tunable magnetic and electronic properties. [ABSTRACT FROM AUTHOR]

With the recent synthesis of two-dimensional (2D) MoSi2N4, the 2D material family with the general formula MA2Z4 has become increasingly popular. However, their topological properties have yet to be explored. Using first-principles calculations, we examine the electronic and topological properties of monolayer MA2Z4 (M = Ca, Sr, or Ba; A = In or Tl; Z = S, Se, or Te) compounds. Our study reveals the quantum spin Hall phase in SrTl2Te4 and BaTl2Te4 with a nontrivial topological bandgap of 97 and 28 meV, respectively, under a hybrid functional approach with the inclusion of spin–orbit coupling. Remarkably, the Z2 topological invariant and the presence of gapless edge states further confirmed their nontrivial topological phase. In addition, we demonstrate the quantized spin Hall conductivity in SrTl2Te4, which stems from the non-zero Berry curvature. The topological phase transition is driven by SOC due to the band inversion between the Te- p x + p y and Tl-s orbitals around Γ. Interestingly, the nontrivial topological properties are robust against strain and preserved under an applied electric field. Finally, our research identifies that the emergent MA2Z4 monolayers have interesting topological properties and have great potential for experimental realization of future topological applications. [ABSTRACT FROM AUTHOR]

A EuZnSb2 antiferromagnetic (AFM) semi metal with a P4/nmm space group (No. 129) is synthesized using the Sb-flux method. The magnetic properties, specific heat, and resistivity of the EuZnSb2 single crystals are analyzed. The magnetic and specific heat properties indicate an antiferromagnetic order of Eu2+ with TN ~ 20 K. The magnetic field is observed to suppress the AFM transition of Eu2+ and the magnetic susceptibility vs. temperature curves exhibit differences when the magnetic field is applied along the ab-plane and c-axis of EuZnSb2 single crystal, reflecting a weak in-plane anisotropy of Eu2+. When the temperature is below 20 K, a spin‒flop transition of the AFM order appears at approximately 1.6 T. The electronic transport measurements indicate that a EuZnSb2 single crystal exhibits metallic properties and an extremely unsaturated positive MR effect. A twofold period of anisotropic magnetoresistance is observed, indicating that the resistivity characteristics correlate with the magnetic field intensity and the angle between the magnetic field direction and the crystallographic axis direction. These studies contribute to enriching the magnetic, specific thermal, and electrical transport properties of EuZnSb2. These results also provide valuable information for further research on other AFM materials. [ABSTRACT FROM AUTHOR]

[Display omitted] High specific-strength lightweight titanium (Ti) alloys, in the absence of interstitial strengthening of oxygen (O) atoms to avoid O-embrittlement, are mainly strengthened via densely semi-coherent nanoprecipitates in the β-matrix that act as dislocation obstacles and often result in high-stress concentrations, contributing to their strength-ductility trade-off. Here, using a low cost Ti-2.8Cr-4.5Zr-5.2Al duplex alloy as a model material, we present a counterintuitive O-doping strategy to create topologically coherent, interstitial-O α′ nanotwinned nanomartensites (NTNMs) with good interfacial strain compatibilities. The interstitial atoms tailor the stress field of edge dislocation cores from planar to non-planar, facilitating multiple variants nucleate simultaneously along O-rich edge dislocations to construct interstitial-O NTNMs. The interstitial-O NTNMs endow our duplex Ti alloys with superior strength of 1.64 gigapascals and large uniform elongation of 11.5%, surpassing all previously reported bulk Ti alloys. This unprecedented combination of mechanical properties is conferred mainly by the interstitial NTNMs, which serve as a sustainable ductility source via a self-hardening deformation mechanism and utilize the pronounced interstitial strengthening of concentrated O atoms. As such, the coherent interstitial NTNMs engineering strategy efficiently combines interstitial solid solution strengthening, and coherent interface strengthening mechanisms, that provides new insights into designing high-strength and large ductility O-tolerant alloys for cost-effective and lightweight applications. [ABSTRACT FROM AUTHOR]

Phytoremediation, including bacteria-assisted phytoremediation, presents a promising technology for treating shooting range soils contaminated with toxic metalloids. In this study, a pot experiment was performed using the halophyte Tamarix smyrnensis and soil collected from a shooting range and artificially spiked at two different antimonite (Sb(III)) concentrations (50 mg/kg and 250 mg/kg) with the aim to explore the Sb phytoremediation of the halophyte. The effect of salt (0.3%) and Mn addition (300 ppm) on its remediation capacity was also investigated. Moreover, the root endophytic community of the halophyte was found able to remove Sb(III) and was periodically inoculated to the plants. The consortium application increased the Sb bioavailable fraction in the soil and enhanced the Sb accumulation in root and aerial parts (up to 50% and 55% respectively at high Sb(III) concentration) compared to the uninoculated plants. Moreover, the presence of Mn increased the translocation factor (21% increase for inoculated and 46% increase for uninoculated plants) while lower TF was observed at high Sb concentrations (0,2 and 0,07 was the lowest value at low and high Sb treatments respectively). The addition of salt, Mn and root endophytic bacteria aided the halophyte to cope with elevated Sb concentrations. The total chlorophyll concentration was higher in inoculated plants compared to the uninoculated ones in all treatments, implying the positive effects of endophytic inoculation. The halophyte T. smyrnensis with the aid of endophytic community presents a promising alternative for remediating shooting range soils especially in areas impacted by salinity. The halophyte T. smyrnensis presents a promising alternative for remediating shooting range soils The application of endophytic bacteria improved the Sb phytoremediation capacity of T. smyrnensis The halophyte T. smyrnensis can be used for Sb phytoextraction in soils impacted by salinity [ABSTRACT FROM AUTHOR]

Magnetoresistance, the change in resistance with applied magnetic fields, is crucial to the magnetic sensor technology. Linear magnetoresistance has been intensively studied in semimetals and semiconductors. However, the air-stable oxides with a large linear magnetoresistance are highly desirable but remain to be fully explored. In this paper, we report the direct observation of linear magnetoresistance in polycrystalline MoO2 without any sign of saturation up to 7 T under 50 K. Interestingly, the linear magnetoresistance reaches as large as 1500% under 7 T at 2 K. The linear field dependence is in great contrast to the parabolic behavior observed in single-crystal MoO2, probably due to phonon scattering near the grain boundaries. Our results pave the way to comprehending magneto-transport behavior in oxides and their potential applications in magnetic sensors. [ABSTRACT FROM AUTHOR]

The precise controllability of the Fermi level is a critical aspect of quantum materials. For topological Weyl semimetals, there is a pressing need to fine-tune the Fermi level to the Weyl nodes and unlock exotic electronic and optoelectronic effects associated with the divergent Berry curvature. However, in contrast to two-dimensional materials, where the Fermi level can be controlled through various techniques, the situation for bulk crystals beyond laborious chemical doping poses significant challenges. Here, we report the milli-electron-volt (meV) level ultra-fine-tuning of the Fermi level of bulk topological Weyl semimetal tantalum phosphide using accelerator-based high-energy hydrogen implantation and theory-driven planning. By calculating the desired carrier density and controlling the accelerator profiles, the Fermi level can be experimentally fine-tuned from 5 meV below, to 3.8 meV below, to 3.2 meV above the Weyl nodes. High-resolution transmission electron microscopy reveals the crystalline structure is largely maintained under irradiation, while electrical transport indicates that Weyl nodes are preserved and carrier mobility is also largely retained. Our work demonstrates the viability of this generic approach to tune the Fermi level in semimetal systems and could serve to achieve property fine-tuning for other bulk quantum materials with ultrahigh precision. [ABSTRACT FROM AUTHOR]

A two-unit symmetrical composite structure with the WSMs defect layer was designed. The energy band and transmission properties are studied based on the transfer matrix theory. Due to the WSMs with the property of time-reversal breaking, the nonreciprocal Tamm states for forward and backward incidence are excited in the interface of the symmetrical composite structure. The numerical results show that the nonreciprocity of the Tamm states is enhanced with an increase in the WSMs thickness. By choosing the appropriate geometric parameters of dielectric layers, two pairs of nonreciprocal dispersive curves are obtained in the two-band gap. The present scenario can be applied in some areas, such as optical isolators and multi-channel nonreciprocal transmission devices. [ABSTRACT FROM AUTHOR]

We prove that a partially hyperbolic attractor for a C 1 vector field with two dimensional center supports an SRB measure. In addition, we show that if the vector field is C 2 , and the center bundle admits the sectionally expanding condition w.r.t. Gibbs u-states, then the attractor can only support finitely many SRB/physical measures whose basins cover Lebesgue almost all points of the topological basin. The proof of these results has to deal with the difficulties which do not occur in the case of diffeomorphisms. [ABSTRACT FROM AUTHOR]

With the recent synthesis of two-dimensional (2D) MoSi2N4, the 2D material family with the general formula MA2Z4 has become increasingly popular. However, their topological properties have yet to be explored. Using first-principles calculations, we examine the electronic and topological properties of monolayer MA2Z4 (M = Ca, Sr, or Ba; A = In or Tl; Z = S, Se, or Te) compounds. Our study reveals the quantum spin Hall phase in SrTl2Te4 and BaTl2Te4 with a nontrivial topological bandgap of 97 and 28 meV, respectively, under a hybrid functional approach with the inclusion of spin–orbit coupling. Remarkably, the Z2 topological invariant and the presence of gapless edge states further confirmed their nontrivial topological phase. In addition, we demonstrate the quantized spin Hall conductivity in SrTl2Te4, which stems from the non-zero Berry curvature. The topological phase transition is driven by SOC due to the band inversion between the Te- p x + p y and Tl-s orbitals around Γ. Interestingly, the nontrivial topological properties are robust against strain and preserved under an applied electric field. Finally, our research identifies that the emergent MA2Z4 monolayers have interesting topological properties and have great potential for experimental realization of future topological applications. [ABSTRACT FROM AUTHOR]

A EuZnSb2 antiferromagnetic (AFM) semi metal with a P4/nmm space group (No. 129) is synthesized using the Sb-flux method. The magnetic properties, specific heat, and resistivity of the EuZnSb2 single crystals are analyzed. The magnetic and specific heat properties indicate an antiferromagnetic order of Eu2+ with TN ~ 20 K. The magnetic field is observed to suppress the AFM transition of Eu2+ and the magnetic susceptibility vs. temperature curves exhibit differences when the magnetic field is applied along the ab-plane and c-axis of EuZnSb2 single crystal, reflecting a weak in-plane anisotropy of Eu2+. When the temperature is below 20 K, a spin‒flop transition of the AFM order appears at approximately 1.6 T. The electronic transport measurements indicate that a EuZnSb2 single crystal exhibits metallic properties and an extremely unsaturated positive MR effect. A twofold period of anisotropic magnetoresistance is observed, indicating that the resistivity characteristics correlate with the magnetic field intensity and the angle between the magnetic field direction and the crystallographic axis direction. These studies contribute to enriching the magnetic, specific thermal, and electrical transport properties of EuZnSb2. These results also provide valuable information for further research on other AFM materials. [ABSTRACT FROM AUTHOR]

Anthropogenic inputs of heavy metals and metalloids pose a risk to wetlands due to their long retention time in sediment, high toxicity at low concentrations, and biological accumulation. This study aimed to assess risk from seven heavy metals (cadmium:Cd, chromium:Cr, copper:Cu, mercury:Hg, nickel:Ni, lead:Pb, zinc:Zn) and one metalloid (arsenic:As) along a trophic pathway by quantifying contaminant loads in muskrat livers, roots of invasive hybrid cattail (Typha x glauca), and in sediment at Horicon National Wildlife Refuge, a wetland of international importance in southeastern Wisconsin, United States. Overall, comparison to literature and thresholds from the Environmental Protection Agency led us to conclude that heavy metals and metalloids pose a low risk to refuge biota with maximum concentrations as follows in sediment, T. x glauca roots, and muskrat livers in mg/kg dry weight: Zn—82, 54, 111, Pb—42, 43, 0.06, Cu—26, 59, 13, Ni—22, 5, 0.7, Cr—20, 3, 0.5, As—6, 11, 0.08, Cd—3, 1, 0.08, Hg—0.1, 0.02, 0.08, a finding which was further supported by low bioconcentration factors between sample types. A spatial analysis using GIS revealed hotspots for Cd, Cr, Cu, Ni, and Zn in sediment in one subplot. However, even in hotspots concentrations mostly fell below protective thresholds and were similar to or lower than concentrations found in a prior survey from 1990 (α < 0.05). Overall, while anthropogenic influences are undoubtedly present, we interpret the concentrations found here to be relatively low and present them as points of comparison regarding risk to plants and mammals for others conducting similar surveys on wetlands. [ABSTRACT FROM AUTHOR]

Two‐dimensional Materials (2DMs) offer significant promise for advancing device miniaturization and extending Moore's law. Despite the challenges posed by high contact resistance in transistors, recent discoveries highlight semimetals as an effective approach for achieving ohmic contact with near‐quantum‐limit contact resistance. The energy band hybridization between semimetal and MoS2 is found to create degenerate states and heavily doped contact, which is proposed as the underlying mechanism responsible for reducing contact resistance. However, a quantitative and comprehensive characterization of the semimetal‐MoS2 interface is lacking, leaving the physical interactions elusive. This study reveals that semimetals induce n‐type doping and tensile strain in monolayer MoS2 grown using CVD, which serve as the contact resistance and mobility boosters. Among the semimetals investigated, including Bismuth (Bi), Antimony (Sb), and their alloy, Bi results in the highest electron doping of 2 × 1013 cm−2 and a 0.5% tensile strain, leading to reduced contact resistance and enhanced mobility. First‐principles calculations and spectroscopy measurements unveil the impact of electron doping and strain in MoS2, and the thermal effects are subsequently explored. This research underscores the potential of semimetals in boosting device performance and lays the foundation for reducing contact resistance in transistors made from 2D materials. [ABSTRACT FROM AUTHOR]

Metals and metalloids (hereafter, metal(loid)s) in plant‐based foods are a source of exposure to humans, but not all metal(loid)‐food interactions are the same. Differences exist between metal(loid)s in terms of their behavior in soils and in how they are taken up by plants and stored in the edible plant tissue/food. Thus, there cannot be one consistent solution to reducing toxic metal(loid)s exposure to humans from foods. In addition, how metal(loid)s are absorbed, distributed, metabolized, and excreted by the human body differs based on both the metal(loid), other elements and nutrients in the food, and the nutritional status of the human. Initiatives like the United States Food and Drug Administration's Closer to Zero initiative to reduce the exposure of young children to the toxic elements cadmium, lead, arsenic, and mercury from foods warrant careful consideration of each metal(loid) and plant interaction. This review explores such plant‐metal(loid) interactions using the example of spinach and the metals cadmium and lead. This review highlights differences in the magnitude of exposure, bioavailability, and the practicality of mitigation strategies while outlining research gaps and future needs. A focus on feasibility and producer needs, informed via stakeholder interviews, emphasizes the need for better analytical testing facilities and grower and consumer education. More research should focus on minimization of chloride inputs for leafy greens to lessen plant‐availability of Cd and the role of oxalate in reducing Cd bioavailability from spinach. These findings are applicable to other leafy greens (e.g., kale, lettuce), but not for other plants or metal(loid)s. Plain Language Summary: Toxic metals like cadmium and lead in foods can be harmful to our health, especially for babies and young children who are more vulnerable due to their smaller size and rapid development. Leafy greens like spinach can absorb these metals from the soil but in different ways. In addition, how and where they accumulate in edible plant tissues also differs. This review uses spinach as an example to compare and contrast how cadmium and lead differ in how they move through soil and accumulate in plant foods. It also discusses practical pre‐ and post‐harvest techniques to lessen human exposure to these metals that can be adopted by producers and consumers. Finally, it highlights future needs and research directions. Key Points: The toxic elements targeted in the Food and Drug Administration Closer to Zero action plan behave differently in soils and in plant uptakeMitigation strategies to reduce exposure to toxic elements must consider the drivers of soil mobility and accumulation into edible tissuesHealth and nutrition factors that affect metal and metalloid bioavailability upon ingestion should also be considered [ABSTRACT FROM AUTHOR]

Sugarcane production has been linked to the release of heavy metals and metalloids (HM/MTs) into the environment, raising concerns about potential health risks. This study aimed to assess the levels of 19 HM/MTs in children living near a sugarcane mill through a pilot biomonitoring investigation. We investigated sex-related differences in these element levels and their correlations. A cross-sectional study was conducted, analyzing data from 20 children in the latter part of 2023. Spearman correlation coefficients with 95% confidence intervals (CIs) were used to assess the relationships between urinary HM/MT levels. Detectable levels of 17 out of the 19 HM/MTs were found across the entire study sample, with arsenic and copper detectable in 95% of the children. Titanium exhibited higher levels in boys compared to girls ( p = 0.017). We identified 56 statistically significant correlations, with 51 of them being positive, while the remaining coefficients indicated negative relationships. This study characterized HM/MT levels in school-aged children residing near a sugarcane mill through a pilot biomonitoring investigation. Further research employing larger sample sizes and longitudinal assessments would enhance our understanding of the dynamics and health impacts of HM/MT exposure in this vulnerable population. [ABSTRACT FROM AUTHOR]

High-sensitivity room-temperature multi-dimensional infrared (IR) detection is crucial for military and civilian purposes. Recently, the gapless electronic structures and unique optoelectrical properties have made the two-dimensional (2D) topological semimetals promising candidates for the realization of multifunctional optoelectronic devices. Here, we demonstrated the in-situ construction of high-performance 1T'-MoTe2/Ge Schottky junction device by inserting an ultrathin AlOx passivation layer. The good detection performance with an ultra-broadband detection wavelength range of up to 10.6 micron, an ultrafast response time of ~ 160 ns, and a large specific detectivity of over 109 Jones in mid-infrared (MIR) range surpasses that of most 2D materials-based IR sensors, approaching the performance of commercial IR photodiodes. The on-chip integrated device arrays with 64 functional detectors feature high-resolution imaging capability at room temperature. All these outstanding detection features have enabled the demonstration of position-sensitive detection applications. It demonstrates an exceptional position sensitivity of 14.9 mV/mm, an outstanding nonlinearity of 6.44%, and commendable trajectory tracking and optoelectronic demodulation capabilities. This study not only offers a promising route towards room-temperature MIR optoelectronic applications, but also demonstrates a great potential for application in optical sensing systems. [ABSTRACT FROM AUTHOR]

Fluoropolymers have weak electroactive properties but are often paired with other materials (inclusions) to form a composite with enhanced electroactive properties and when those inclusions are a metal or metalloid fuel (e.g., Al, Si, B) they can then function as electroactive reactive materials. There is strong interest in understanding the electromechanical (piezo, flexo, dielectric) properties toward the development of multifunctional energetics. Specifically, in this effort, we report the influence of magnesium diboride (MgB2) on the electroactive and combustion properties in a composite system with the fluoropolymer tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride (THV). The dielectric, flexoelectric, piezoelectric, burning rate, and heat of reaction are investigated for composites with 50–70 wt. % MgB2 loading. It is observed that with an increase in solids loading that the dielectric, flexoelectric, and burning rate increase. For example, at 70 wt. % MgB2, the measured dielectric constant was 298 ± 10, and the flexoelectric coefficient was 16.6 ± 1.2 nC/m. Unexpectedly, a true piezoelectric coefficient (d33) was measured between 11.4 ± 0.2 and 13.0 ± 0.3 pC/N at these solids loadings. Due to the mechanical properties of these composite systems, an apparent piezoelectric coefficient of 108 pC/N was calculated indicating that these reactive materials are highly electroactive. The multifunctional properties are demonstrated by applying the force of the human body (via jumping) to a THV/MgB2 (50 wt. %) film. A peak voltage of 0.75 V was observed. This work indicates that a variety of reactive materials may offer multifunctional capabilities. [ABSTRACT FROM AUTHOR]

The crystallization temperature of deeply undercooled Cu–Ge alloy melts is repeatedly measured. A statistical analysis is applied on the undercooling distributions obtained from nine different compositions, ranging from the pure semimetal (Ge) to the pure metal (Cu). By considering each undercooling distribution as an inhomogeneous Poisson process, the nucleation rates for every composition are calculated. The Thompson–Spaepen model for homogeneous nucleation in binary alloys is applied, enabling the estimation of nucleation parameters, such as kinetic pre-factors and interfacial energies, as a function of composition. Furthermore, the Turnbull coefficient α, a dimensionless solid–liquid interfacial energy constant, is also calculated as a function of alloy constitution, suggesting a dependence on the liquid composition. The composition-dependent changes of α are of considerable importance, since the α is originally defined for pure systems as a quantity dependent on crystal structure, and is nevertheless used for describing nucleation kinetics of binary and glass forming multi-component alloy systems. [ABSTRACT FROM AUTHOR]

Nodal link semimetals as a type of topological semimetals are characterized by the nodal link rings in the Brillouin zone. The magneto-optical conductivity of nodal link semimetals is investigated numerically based on a system with a magnetic field. We find that in the system, the Landau levels (LLs) and magnetic field show a relationship of three halves power, which can lead to an intricate curved LLs. Due to the rich structure of LLs, we divided the LLs into four different regions to calculate the magneto-optical conductivity. We calculated the absorption peaks of longitudinal and Hall conductance of a neutral system and with different chemical potential. We find that the absorption peaks of longitudinal conductance are in a curved background in the whole range of magnetic field. When chemical potential is tuned to pass through the LLs, there are not only the intraband transition but also weak redistributed peaks in the low frequency. From the transition peaks of Hall conductance, we can find that there are several negative peaks because of the striking LLs spectrum structure. This will provide a feasible way to distinguish nodal link semimetals from other materials. [ABSTRACT FROM AUTHOR]

We present a theoretical study of the optical absorption coefficient Urbach tail broadening parameter Γ behavior in the Hg1−xCdxTe alloy semiconductor in the 0.21 ≤ x ≤ 0.6 alloy composition interval. This x interval corresponds to the very attractive 0.10 ≤ EG≤ 0.75 eV medium infrared (MIR) and far infrared (FIR) optical ranges. We compare two absorption coefficient nonparabolic models based on Kane 4-band formalism, one including the Burstein–Moss shift called the NPBM-model and the other one without and called the NP-model. By comparing the results of both models with existing experimental and theoretical data, we show the strong nonparabolic behavior of the absorption coefficient in Hg1−xCdxTe in agreement with previous studies. The best fitting is obtained with the NPBM-model, where Γ is used as an adjustable parameter varying with x, temperature (T), and photon energy (ħω) in the E ≤ EG sub-bandgap energy range. With decreasing x, Γ is found to increase first slightly with x in the 0.443 ≤ x ≤ 0.6 MIR range and then strongly and nonlinearly in the 0.21 ≤ x < 0.443 FIR range. These unusual Γ(x, ħω) dependences suggest a strong influence of nonparabolicity and band state mixing effects, which become strongly enhanced in the FIR range between strongly interacting and almost overlapping bands as x tends to 0.16 of the critical value, making Hg1−xCdxTe experience a semiconductor–semimetal transition. [ABSTRACT FROM AUTHOR]

Progress on two-dimensional materials has shown that valleys, as energy extrema in a hexagonal first Brillouin zone, provide a new degree of freedom for information manipulation. Then, valley Hall topological insulators supporting such-polarized edge states on boundaries were set up accordingly. In this paper, a two-dimensional valley crystal composed of six tunable dielectric triangular pillars in each unit cell is proposed in the photonic sense of a deformed Su–Schrieffer–Heeger model. We reveal the vortex nature of valley states and establish the selection rules for valley-polarized states. Based on the valley topology, a rhombus-shaped beam splitter waveguide is designed to verify the valley-chirality selection rule above. Our numerical results entail that this topologically protected edge states still maintain robust transmission at sharp corners, thus providing a feasible idea for valley photonic devices in the THz regime. [ABSTRACT FROM AUTHOR]

The Andreev reflection in topological nodal-line semimetal–superconductor (TNLSM–SC) junctions is studied based on the Landauer–Büttiker formula combined with the non-equilibrium Green's function method. It is found that the Andreev reflection coefficient can reach large values of several tens for a TNLSM–SC junction. In the energy gap, two new peaks for the Andreev reflection appear. Outside the energy gap, the Andreev reflection shows a quasi-periodic variation. With the incident energy increasing, the Andreev reflection decreases periodically. This phenomenon originates from the peculiar energy spectrum of the TNLSMs. The value and quasi-period of the Andreev reflection coefficient depend on the size of the system in different directions. These anomalous Andreev reflections are helpful to study the transport properties in normal metal–superconductor junctions. [ABSTRACT FROM AUTHOR]

Topological insulators possess non-conductive bulk and present surface states, henceforth, they are electrically conductive along their boundaries. Bismuth selenide (Bi2Se3) is one of the most promising topological insulators. However, a major drawback is its n-type nature arising from its natural doping, which makes the transport in the bulk dominant. This effect can be overcome by shifting the chemical potential into the bandgap, turning the transport of the surface states to be more pronounced than the bulk counterpart. In this work, Bi2Se3 was grown by molecular beam epitaxy and doped with 0.8, 2, 7, and 14 at. % of Ga, with the aim of shifting the chemical potential into the bandgap. The structural, morphological, and electronic properties of the Ga doped Bi2Se3 are studied. Raman and x-ray diffraction measurements confirmed the incorporation of the dopants into the crystal structure. Transport and magnetoresistance measurements in the temperature range of 1.5–300 K show that Ga-doped Bi2Se3 is n-type with a bulk charge carrier concentration of 1019 cm−3. Remarkably, magnetotransport of the weak antilocalization effect measurements confirms the existence of surface states up to a doping percentage of 2 at. % of Ga and coherence length values between 50 and 800 nm, which envisages the possibility of topological superconductivity in this material. [ABSTRACT FROM AUTHOR]