Search

MnBi2Te4 is a van der Waals topological insulator with intrinsic intralayer ferromagnetic exchange and A-type antiferromagnetic interlayer coupling. Theoretically, it belongs to a class of structurally centrosymmetric crystals whose layered antiferromagnetic order breaks inversion symmetry for even layer numbers, making optical second harmonic generation (SHG) an ideal probe of the coupling between the crystal and magnetic structures. Here, we perform magnetic field and temperature-dependent SHG measurements on MnBi2Te4 flakes ranging from bulk to monolayer thickness. We find that the dominant SHG signal from MnBi2Te4 is unexpectedly unrelated to both magnetic state and layer number. We suggest that surface SHG is the likely source of the observed strong SHG, whose symmetry matches that of the MnBi2Te4-vacuum interface. Our results highlight the importance of considering the surface contribution to inversion symmetry-breaking in van der Waals centrosymmetric magnets.

A topological insulator (TI) interfaced with an s-wave superconductor has been predicted to host an unusual form of superconductivity known as topological superconductivity (TSC). Molecular beam epitaxy (MBE) has been the primary approach in the scalable synthesis of the TI/superconductor heterostructures. Although the growth of epitaxial TI films on s-wave superconductors has been achieved, it remains an outstanding challenge for synthesizing atomically thin TI/superconductor heterostructures, which are critical for engineering the TSC phase. Here, we used MBE to grow Bi2Se3 films with the controlled thickness on monolayer NbSe2 and performed in-situ angle-resolved photoemission spectroscopy and ex-situ magneto-transport measurements on these Bi2Se3/monolayer NbSe2 heterostructures. We found that the emergence of Rashba-type bulk quantum well bands and spin-nondegenerate surface states coincides with a marked suppression of the in-plane upper critical magnetic field of the superconductivity in Bi2Se3/monolayer NbSe2 heterostructures. This is the signature of a crossover from Ising- to Rashba-type superconducting pairings, induced by altering Bi2Se3 film thickness. Our work opens a new route for exploring a robust TSC phase in TI/Ising superconductor heterostructures., 27 pages, 4 pages, comments are welcome

Background Colonization of carbapenem-resistant Enterobacterale (CRE) is considered as one of vital preconditions for infection, with corresponding high morbidity and mortality. It is indispensable to construct a reliable prediction model and develop preventive and therapeutic strategies for those high-risk infected CRE carriers. Methods A retrospective cohort study was conducted in two Chinese tertiary hospitals for patients with CRE colonization from 2011 to 2021. Univariate analysis and the Fine-Gray subdistribution hazard model were utilized to identify potential risk factors for CRE-colonized infection, while death was the competing event. A nomogram was established to predict 30-day and 60-day risk of CRE-colonized infection. Results 879 eligible patients were enrolled in our study and divided into training (n = 761) and validation (n = 118) group, respectively. There were 196 (25.8%) patients suffered from subsequent CRE infection within 20 (interquartile range [IQR], 14–32) days after detection of colonization. Multisite colonization, polymicrobial colonization, catheterization and receiving albumin after colonization, concomitant respiratory diseases, receiving carbapenems and antimicrobial combination therapy before CRE colonization within 90 days were reserved in final model. Model discrimination and calibration were acceptable for predicting the probability of 60-day CRE-colonized infection in both training (area under the curve [AUC], 74.7) and validation dataset (AUC, 81.1). Decision-curve analysis revealed a significantly better net benefit in current model. Our prediction model is freely available online at https://ken-zheng.shinyapps.io/PredictingModelofCREcolonizedInfection/. Conclusions Our nomogram has a favorable predictive performance, which is deemed as a meaningful clinical tool for early identification of CRE carriers in high-risk status of subsequent infection.

Growth of 2D materials under ultrahigh-vacuum (UHV) conditions allows for an in situ characterization of samples with direct spectroscopic insight. Heteroepitaxy of transition-metal dichalcogenides (TMDs) in UHV remains a challenge for integration of several different monolayers into new functional systems. In this work, we epitaxially grow lateral WS2–MoS2 and vertical WS2/MoS2 heterostructures on graphene. By means of scanning tunneling spectroscopy (STS), we first examined the electronic structure of monolayer MoS2, WS2, and WS2/MoS2 vertical heterostructure. Moreover, we investigate a band bending in the vicinity of the narrow one-dimensional (1D) interface of the WS2–MoS2 lateral heterostructure and mirror twin boundary (MTB) in the WS2/MoS2 vertical heterostructure. Density functional theory (DFT) is used for the calculation of the band structures, as well as for the density of states (DOS) maps at the interfaces. For the WS2–MoS2 lateral heterostructure, we confirm type-II band alignment and determine the corresponding depletion regions, charge densities, and the electric field at the interface. For the MTB, we observe a symmetric upward bend bending and relate it to the dielectric screening of graphene affecting dominantly the MoS2 layer. Quasi-freestanding heterostructures with sharp interfaces, large built-in electric field, and narrow depletion region widths are proper candidates for future designing of electronic and optoelectronic devices.

One-dimensional (1D) topologically protected states are usually formed at the interface between two-dimensional (2D) materials with different topological invariants. Therefore, 1D chiral interface channels (CICs) can be created at the boundary of two quantum anomalous Hall (QAH) insulators with different Chern numbers. Such a QAH junction can function as a chiral edge current distributer at zero magnetic field, but its realization remains challenging. Here, by employing an in-situ mechanical mask, we use molecular beam epitaxy (MBE) to synthesize QAH insulator junctions, in which two QAH insulators with different Chern numbers are connected along a 1D junction. For the junction between C = 1 and C = -1 QAH insulators, we observe quantized transport and demonstrate the appearance of the two parallel propagating CICs along the magnetic domain wall at zero magnetic field. Moreover, since the Chern number of the QAH insulators in magnetic topological insulator (TI)/TI multilayers can be tuned by altering magnetic TI/TI bilayer periods, the junction between two QAH insulators with arbitrary Chern numbers can be achieved by growing different periods of magnetic TI/TI on the two sides of the sample. For the junction between C = 1 and C = 2 QAH insulators, our quantized transport shows that a single CIC appears at the interface. Our work lays down the foundation for the development of QAH insulator-based electronic and spintronic devices, topological chiral networks, and topological quantum computations., 20 pages, 4 figures, comments are welcome

Although highly dispersed, critical Re metal has attracted lots of attention from geoscientists, the controlling factors of Re-content variation are not completely understood, especially with regards to the genetic relationship between Re-bearing Mo polymetallic deposits and plate subduction evolution. It is well documented that the South China Mo Province, in Zhejiang Province, is characterized by multi-stage Mo polymetallic mineralization associated with Paleo-Pacific plate subduction. The Xianlin Mo(Cu)–Fe deposit occurs in Western Zhejiang as porphyry mineralization or skarn mineralization between the granodiorite and limestone. Zircon U–Pb analysis of the ore-forming granodiorite yields a Concordia age of 150.8 ± 1.1 Ma. Six molybdenite samples have relatively high Re contents (128.9~155.7 ppm) and deliver a weighted mean model age of 149.6 ± 1.3 Ma. These geochronological data suggest the Xianlin polymetallic mineralization was genetically related to the granodiorite in the Late Jurassic. Moreover, a new compilation of reliable Re contents and Re–Os isotope age data in Zhejiang Province indicates a decreasing trend in Re contents of molybdenite from the Jurassic Fe-/Cu-dominated Mo mineralization stage to the Cretaceous PbZn-enriched Mo mineralization stage in the South China Mo Province. Based on previously proposed models relating tectonic, magmatic, and hydrothermal processes, it is suggested that the Jurassic Re-enriched Mo mineralization, associated with I-type granitoids, formed in a compressive setting during the low-angle subduction of the Paleo-Pacific slab, whilst the Cretaceous Re-poorer Mo/Mo–Pb–Zn mineralization, related to both I- and A-type granitoids, formed in an extensional back-arc setting triggered by the rollback of the Paleo-Pacific slab.

The design of high-performance and low-cost oxygen evolution reaction (OER) electrocatalysts is crucial for environment friendly hydrogen production. Some transition metals have been proven to be good substitutes for noble metals due to their unique electronic structural characteristics and good electrocatalytic performances, with examples including nickel and cobalt, which are usually used to prepare OER electrocatalysts. In this work, we synthesized three-dimensional Ni-Co-Fe ternary layered double hydroxide nanosheet array electrocatalysts via hydrothermal process. Iron element was introduced into the Ni-Co based hydroxide. The ternary layered double hydroxide has a nanoarrays microstructure. Theoretical analysis confirms that by adjusting the ratio of Ni/Co/Fe, the microstructure of the catalyst changes significantly. Attributed to the special nanostructure, the catalysts show superior catalytic activities in oxygen evolution reaction (OER). The results show that a small overpotential of 222 mV at the current density of 20 mA·cm−2 for the OER in 1.0 M KOH is acquired. A small Tafel slope of 61.22 mVdec−1 and a maximum specific capacitance of 239 Fg−1 are also obtained.

Aim: To observe the difference in the risk of polymyxin B (PMB)-induced acute kidney injury (AKI) with or without dose adjustment based on the patients renal function. Materials & methods: This retrospective cohort analysis was carried out in 115 patients treated with PMB from November 2018 to October 2019. Results: No significant difference in the incidence of AKI as well as secondary outcomes was observed between these two groups (47.5 vs 37.14%; p = 0.304). Conclusion: Dosing adjustment based on renal function does not significantly lower the risk of PMB-induced AKI. A non adjusted dosing strategy for PMB is recommended in patients exhibiting various levels of renal impairment.

Considering the importance of ceftazidime/avibactam (CAZ/AVI) and polymyxin B (PMB) in treating carbapenem-resistant Klebsiella pneumoniae (CRKP) infection, it is essential to evaluate the efficacy and safety of these agents and provide appropriate medical advice to clinical specialists.We conducted a retrospective cohort study in two Chinese tertiary hospitals for critically ill patients with CRKP infection who received at least 24-h CAZ/AVI-based or PMB-based treatment. A binary logistic model and a Cox proportional hazards regression model were constructed to analyze variables that could potentially affect 30-day microbiological eradication and all-cause mortality, respectively.From January 2019 to December 2021, 164 eligible patients were divided into CAZ/AVI and PMB cohorts. A notably lower 30-day mortality rate (35.4% vs 69.5%, P 0.001) and a higher 30-day microbiological eradication rate (80.5% vs 32.9%, P 0.001) were observed for patients receiving CAZ/AVI-based treatment, compared with cases in the PMB group. A longer antimicrobial treatment duration ( 7 days) could also significantly decrease the mortality rate and increase the microbiological eradication rate. Female patients had a higher survival rate than male patients. Age over 65 years, sepsis, continuous renal replacement therapy, and organ transplantation were identified as negative factors for survival. In the subgroup analysis, CAZ/AVI combined with tigecycline or amikacin could effectively lower mortality. According to safety evaluation results, potential elevation of hepatic enzymes was associated with CAZ/AVI-based treatment, while renal impairment was probably related to PMB-based treatment.CAZ/AVI was more effective than PMB in treating CRKP-infected patients. Tigecycline and amikacin were proven to be beneficial as concomitant agents in combination with CAZ/AVI. A treatment period lasting over 7 days was recommended. Hepatoxicity of CAZ/AVI and nephrotoxicity of PMB should be monitored carefully. Further well-designed studies should be performed to verify our conclusion.

The flat bands that appear in some twisted van der Waals heterostructures provide a setting in which strong interactions between electrons lead to a variety of correlated phases1–20. In particular, heterostructures of twisted double bilayer graphene host correlated insulating states that can be tuned by both the twist angle and an external electric field11–14. Here, we report electrical transport measurements of twisted double bilayer graphene with which we examine the fundamental role of spontaneous symmetry breaking in its phase diagram. The metallic states near each of the correlated insulators exhibit abrupt drops in their resistivity as the temperature is lowered, along with associated nonlinear current–voltage characteristics. Despite qualitative similarities to superconductivity, the simultaneous reversals in the sign of the Hall coefficient point instead to spontaneous symmetry breaking as the origin of the abrupt resistivity drops, whereas Joule heating seems to underlie the nonlinear transport. Our results suggest that similar mechanisms are probably relevant across a broader class of semiconducting flat band van der Waals heterostructures. Transport measurements show that spontaneous symmetry breaking plays a crucial role in the correlated insulating and metallic states in twisted double bilayer graphene.

We determined the structure of epitaxial $2H\text{\ensuremath{-}}\mathrm{Ta}{\mathrm{S}}_{2}$ on Au(111) using the method of x-ray standing waves (XSW), supported by density functional theory (DFT) calculations and scanning tunneling microscopy (STM). The lattice mismatch between substrate and overlayer gives rise to a moir\'e superstructure, which modulates the structural and electronic properties. For a specific registry (S atoms directly above Au substrate atoms), local covalentlike bonds form, whereas globally weak van der Waals bonding prevails. Still, the $\mathrm{Ta}{\mathrm{S}}_{2}$ layer remains rather flat. Significant charge transfer from Au(111) into the conduction band of the two-dimensional material is found.

Growth of 2D materials under ultrahigh-vacuum (UHV) conditions allows for an in situ characterization of samples with direct spectroscopic insight. Heteroepitaxy of transition-metal dichalcogenides (TMDs) in UHV remains a challenge for integration of several different monolayers into new functional systems. In this work, we epitaxially grow lateral WS

The moir\'e pattern of hBN/Ru(0001) provides a template for the adsorption of the alkali metals Cs and K: Scanning tunneling microscopy reveals that the adatoms prefer to adsorb in the valley areas of the moir\'e unit cell. Distinctive from transition metal adatoms that tend to agglomerate, the alkali metal adatoms avoid each other within the valleys, leading to a sharper distribution than the Poisson statistics expected for noninteracting particles. This sub-Poissonian distribution is further explored via Monte Carlo simulations. The average charge $q$ of the alkali metal adatoms is extracted for different alkali metal concentrations $\ensuremath{\lambda}$, which reveals a monotonically decreasing $q(\ensuremath{\lambda})$ dependence. We explain this dependence with the energy trade-off between the charge transfer from the alkali metals to the more electron-affine Ru(0001) substrate and the static electric field created by this charge transfer.

There has been increased development of assistive robots for the home, along with empirical studies assessing cultural differences on user perception. However, little attention has been paid to cultural differences with respect to non- humanoid, multi-robot interactions in homes or otherwise. In this exploratory paper, we investigate how cultural differences may impact users’ preferences and perceived usefulness of a multi-robot system by creating an interactive online survey and considering variables often absent in HRI studies. We introduce our multi-robot design and survey construction, and report results evaluated across 191 young adult participants from China, India, and the USA. We find significant effects of culture on both participants’ preferences and perceived usefulness of the system between India and China or the USA, but not between China and the USA. We also find effects of culture on perceived usefulness to be partially mediated by participant preferences. Our findings reinforce the importance of considering cultural differences in designing domestic multi-robotic assistants.

The interplay between band topology and magnetism can give rise to exotic states of matter. For example, magnetically doped topological insulators can realize a Chern insulator that exhibits quantized Hall resistance at zero magnetic field. While prior works have focused on ferromagnetic systems, little is known about band topology and its manipulation in antiferromagnets. Here, we report that MnBi$_2$Te$_4$ is a rare platform for realizing a canted-antiferromagnetic (cAFM) Chern insulator with electrical control. We show that the Chern insulator state with Chern number $C = 1$ appears as soon as the AFM to canted-AFM phase transition happens. The Chern insulator state is further confirmed by observing the unusual transition of the $C = 1$ state in the cAFM phase to the $C = 2$ orbital quantum Hall states in the magnetic field induced ferromagnetic phase. Near the cAFM-AFM phase boundary, we show that the Chern number can be toggled on and off by applying an electric field alone. We attribute this switching effect to the electrical field tuning of the exchange gap alignment between the top and bottom surfaces. Our work paves the way for future studies on topological cAFM spintronics and facilitates the development of proof-of-concept Chern insulator devices., 13 pages, 4 figures, and 5 supplementary figures. Comments are welcome

A coin-shaped porous carbon is produced by carbonization of Al-based metal-organic frameworks and followed by the removal of Al2O3 though dissolving in NaOH solution. The hierarchically porous carbon has a large surface area (1,508 m2 g−1) with suitable size of mesopores (6.35 nm). The material exhibits an increased specific capacitance of 323 F g−1 at 1 mV s−1. It also has excellent high current discharge performance and superior stability with 97.9% retention at an ultra-high current density of 100 A g−1 during 15 × 104 cycles. The constructed symmetric solid supercapacitor shows an appreciably large capacitance of up to 117.2 F g−1 at 0.2 A g−1, corresponding to the high energy density of 36.5 W h kg−1 within a voltage window of 1.5 V. In addition, it offers satisfied durability with 11.5% decay rate after 20,000 cycles. The carbon with improved electrochemical properties is most likely attributed to its special coin shape and hierarchically porous pores. It is a new potential strategy to configure unique structure porous carbon materials for power supercapacitors via metal-organic frameworks serving as precursors.

Nano-Ag4Bi2O5/MnOx@rGO ternary composite was prepared via a facile coprecipitation method in rGO dispersed concentrated KOH solution under precisely controlled conditions. Morphology characterizations indicate that the Ag4Bi2O5/MnOx composite with corncob-like shape of 200 nm in length and 50 nm in width is loaded on the wrinkled rGO. The electrochemical tests find that the optimized ternary catalyst with 60% rGO contained offers much higher initial potential (0.0799 V vs. Hg/HgO) and limiting current density (6.164 mA cm−2) than that of the standardized Pt/C (0.017 V and 5.09 mA cm−2) at a rotation rate of 1600 rpm. Furthermore, the catalyst possesses preferable durability and anti-methanol as compared with Pt/C. The Ag4Bi2O5/MnOx/rGO with surperior ORR properties indicates that it will be a promising catalyst for oxygen reduction reaction in alkaline electrolyte.

Nitrogen-doped porous carbon is prepared by the fusion and carbonization processes of Al-based metal-organic frameworks and melamine, and following removal of thermal decomposed Al 2 O 3 via dissolving in NaOH solution. The hierarchically porous carbon has a large surface area of 1452 m 2 g −1 with mesopores of suitable size (4.64 nm). It exhibits an enhanced specific capacitance and rate capability of 318.7 F g −1 (1 A g −1 ) and 210.5 F g −1 (100 A g −1 ), respectively. The cycling life tests indicate the material offers superior stability with 96.4% retention at ultra-high current density of 100 A g −1 during 50, 000 cycles. The improved electrochemical properties of this carbon can be attributed to the exogenous nitrogen-doping, special ellipsoid shape and hierarchically porous structure. This method is a new potential strategy to configure unique structure and particular heteroatom-doped porous carbon material for power supercapacitors via the fusion of metal-organic frameworks and heteroatom-containing polymer.

We studied the effect of alkali metal intercalation (Cs and Li) on the geometry of graphene on Ir(111) using the X-ray standing waves technique. For both alkali metals, the increase in the mean hei...