Anomalous thermal Hall effect and anomalous Nernst effect of CsV3_{3}Sb5_{5}

Motived by time-reversal symmetry breaking and giant anomalous Hall effect in kagome superconductor \textit{A}V$_3$Sb$_5$ (\textit{A} = Cs, K, Rb), we carried out the thermal transport measurements on CsV$_3$Sb$_5$. In addition to the anomalous Hall effect, the anomalous Nernst effect and the anomalous thermal Hall effect emerge. Interestingly, the longitudinal thermal conductivity $\kappa_{xx}$ largely deviates from the electronic contribution obtained from the longitudinal conductivity $\sigma_{xx}$ by the Wiedemann-Franz law. In contrast, the thermal Hall conductivity $\kappa_{xy}$ is roughly consistent with the Wiedemann-Franz law from electronic contribution. All these results indicate the large phonon contribution in the longitudinal thermal conductivity. Moreover, the thermal Hall conductivity is also slightly greater than the theoretical electronic contribution, indicating other charge neutral contributions. More than that, the Nernst coefficient and Hall resistivity show the multi-band behavior with possible additional contribution from Berry curvature at the low fields

Vanadium-Based Superconductivity in a Breathing Kagome Compound Ta2V3.1Si0.9

Superconductivity in V-based kagome metals has recently raised great interest as they exhibit the competing ground states associated with the flat bands and topological electronic structures. Here we report the discovery of superconductivity in Ta2V3.1Si0.9 with a superconducting transition temperature Tc of 7.5 K, much higher than those in previously reported kagome metals at ambient pressure. While the V ions form a two-dimensional breathing kagome structure, the length difference between two different V-V bonds is just 0.04, making it very close to the perfect kagome structure. Our results show that Ta2V3.1Si0.9 is a moderate-coupled superconductor with a large upper critical field that is close to the Pauli limit. DFT calculations give a van-Hove-singularity band located at Fermi energy, which may explain the relatively high Tc observed in this material.Comment: 19 pages, 5 figure

Spectroscopic Evidence for a Three-Dimensional Charge Density Wave in Kagome Superconductor CsV3_3Sb5_5

The recently discovered AV3Sb5 (A=K, Rb, Cs) family, possessing V kagome nets, has received considerable attention due to the topological electronic structure and intriguing correlated phenomena, including an exotic charge density wave (CDW) and superconductivity. Detailed electronic structure studies are essential to unravel the characteristics and origin of the CDW as well as its interplay with superconductivity. Here, we present angle-resolved photoemission spectroscopy (ARPES) measurements for CsV3Sb5 at multiple temperatures and photon energies to reveal the nature of the CDW from an electronic structure perspective. We present evidence for a three-dimensional (3D) CDW order. In the process we also pinpoint a surface state attributed to a Cs terminated surface. This state was previously attributed to band folding band due to a CDW along the c direction or a quantum well state from quantum confinement. The CDW expected 2-fold lattice reconstruction along c axis is observed to be a quadrupling of the unit cell, thus for the first time directly demonstrating the 3D nature of the CDW from the electronic structure perspective. Moreover, this 3D CDW configuration originates from two distinct types of distortions in adjacent kagome layers. These present results not only provide key insights into the nature of the unconventional CDW in CsV3Sb5 but also provides an important reference for further studies on the relationship between the CDW and superconductivity.Comment: 19 pages, 4 figure

Testing Electron-phonon Coupling for the Superconductivity in Kagome Metal CsV3Sb5\rm{CsV_3Sb_5}

In crystalline materials, electron-phonon coupling (EPC) is a ubiquitous many-body interaction that drives conventional Bardeen-Cooper-Schrieffer superconductivity. Recently, in a new kagome metal $\rm{CsV_3Sb_5}$, superconductivity that possibly intertwines with time-reversal and spatial symmetry-breaking orders is observed. Density functional theory calculations predicted weak EPC strength,$\lambda$, supporting an unconventional pairing mechanism in $\rm{CsV_3Sb_5}$. However, experimental determination of $\lambda$ is still missing, hindering a microscopic understanding of the intertwined ground state of $\rm{CsV_3Sb_5}$. Here, using 7-eV laser-based angle-resolved photoemission spectroscopy and Eliashberg function analysis, we determine an intermediate $\lambda$=0.45~0.6 at T=6 K for both Sb 5p and V 3d electronic bands, which can support a conventional superconducting transition temperature on the same magnitude of experimental value in $\rm{CsV_3Sb_5}$. Remarkably, the EPC on the V 3d-band enhances to $\lambda$~0.75 as the superconducting transition temperature elevated to 4.4 K in $\rm{Cs(V_{0.93}Nb_{0.07})_3Sb_5}$. Our results provide an important clue to understand the pairing mechanism in the Kagome superconductor $\rm{CsV_3Sb_5}$.Comment: To appear in Nature Communication

Three-Dimensional Flat Bands and Dirac Cones in a Pyrochlore Superconductor

Emergent phases often appear when the electronic kinetic energy is comparable to the Coulomb interactions. One approach to seek material systems as hosts of such emergent phases is to realize localization of electronic wavefunctions due to the geometric frustration inherent in the crystal structure, resulting in flat electronic bands. Recently, such efforts have found a wide range of exotic phases in the two-dimensional kagome lattice, including magnetic order, time-reversal symmetry breaking charge order, nematicity, and superconductivity. However, the interlayer coupling of the kagome layers disrupts the destructive interference needed to completely quench the kinetic energy. Here we experimentally demonstrate that an interwoven kagome network--a pyrochlore lattice--can host a three dimensional (3D) localization of electron wavefunctions. In particular, through a combination of angle-resolved photoemission spectroscopy, fundamental lattice model and density functional theory (DFT) calculations, we present the novel electronic structure of a pyrochlore superconductor, CeRu$_2$. We find striking flat bands with bandwidths smaller than 0.03 eV in all directions--an order of magnitude smaller than that of kagome systems. We further find 3D gapless Dirac cones predicted originally by theory in the diamond lattice space group with nonsymmorphic symmetry. Our work establishes the pyrochlore structure as a promising lattice platform to realize and tune novel emergent phases intertwining topology and many-body interactions.Comment: 12 pages, 3 figure

Research on the Construction of Manufacturing Industry Chain Ecosystem—A Case Study of Tianjin Manufacturing Industry

This study takes Tianjin as an example to analyze how to build the manufacturing industry chain ecosystem. Based on the ecosystem theory, the related literature of manufacturing industry chain and value chain, and combined with various action plans for the development of manufacturing industry in Tianjin, the structure chart and construction roadmap of industrial chain ecosystem were drawn. Based on the input–output data of 42 sectors in Tianjin, this study calculated and analyzed the changes in embedment degree of various manufacturing industries in Global Value Chain (GVC) and National Value Chain (NVC) in Tianjin from 2010 to 2017. It is found that the industrial chain ecosystem is mainly composed of four elements: the enterprises on the industrial chain, the information flowing among enterprises, the goods circulating among enterprises, and the external environment of enterprises. The connection of supply and demand chains, enterprise chains, space chains and value chains forms an industrial chain, and the value chain is a crucial relationship chain in the connection mechanism. In addition, 2015 is a turning point for Tianjin manufacturing industry to embed in GVC and NVC, mainly due to the industrial economic adjustment in Tianjin, the global economic turmoil, and the establishment of the manufacturing industrial park. In terms of R&D intensity, high and medium high-tech manufacturing industries tend to be embedded in GVC, but are easily affected by enterprises and environmental factors. However, low and medium low-tech manufacturing industries still have ample space to integrate into GVC, information and products are important factors to determine the upgrading of its industrial chain. Therefore, in order to better construct the industrial chain ecosystem of manufacturing industry and enhance the industrial competitiveness of Tianjin’s manufacturing industry, it is necessary to give priority to the development of high-tech manufacturing industry, expand the international openness of low-tech manufacturing industry, support regional advantageous industries, and carry out dynamic regulation of industrial ecology

How Do Transportation Influencing Factors Affect Air Pollutants from Vehicles in China? Evidence from Threshold Effect

In recent years, China has promoted a series of legal norms to reduce the environmental impact of air pollutants from vehicles. The three main vehicle emission species (carbon monoxide, hydrocarbons, nitrogen oxides) contribute significantly to air pollution. In this study, the emission factor method was used to estimate air pollutants from vehicles in 31 provinces from 2006 to 2016. The results show a trend of total vehicle carbon monoxide (CO) and hydrocarbons (HC) emissions decreasing with time; the vehicle nitrogen oxides (NOx) emission trend is divided into two stages: an upward trend between 2006 and 2012 and a downward trend after 2012. Based on a panel threshold, a regression method was used to divide the vehicle NOx and CO emissions in China into four emission zones: low emissions, medium emissions, high emissions, and extra-high emissions. Vehicle HC emissions were divided into three emission zones, which corresponded to low emissions, medium emissions, and high emissions. Overall, vehicle pollution emission efficiency and per capita GDP have a significant inhibitory effect on the three main air pollutants from vehicles (NOx, HC, CO). Both passenger and freight turnover have significant roles in promoting the three air pollutants from vehicles (NOx, HC, CO). Road density and road carrying capacity have a significant role in promoting vehicle HC and CO emissions. Increasing truck proportion inhibits vehicle CO emissions and promotes vehicle NOx emissions. The urbanization rate has a positive effect on vehicle HC and CO emissions. Moreover, there is obvious heterogeneity in different emission zones of the three air pollutants from vehicles (NOx, HC, CO)

Application of a mixture model to assess the effect of measles-mumps-rubella vaccine on the mumps epidemic in children from kindergarten to early school age in Jiangsu Province, China

A single dose of the measles-mumps-rubella (MMR) vaccine has been applied in routine immunizations for children in China; however, the Immunoglobulin G (IgG) antibody level of mumps in children from kindergarten to early school age with MMR vaccine immunization history has not been elucidated. This study aimed to describe the immunity profile of children from kindergarten to early school age to identify the susceptible population. In Jiangsu Province, a cross-sectional survey of 4- to 8-year-old children who were vaccinated with at least one dose of MMR vaccine was conducted. IgG antibody results were analyzed by employing both the Enzyme-Linked Immunosorbent Assay (ELISA) cutoff values and the mixture model. A total of 7436 eligible subjects were enrolled: 3386 subjects were in kindergarten, and 4450 were in primary school. The overall seroprevalence (75.4%, 95% CI: 74.4%-76.4%) and Geometric mean concentration (GMC, 201.4U/ml, 95% CI: 194.1–209.4) of mumps antibodies in 2016 were low. The seroprevalence of children in kindergarten (78.1%, 95% CI: 76.6%-79.4%) was significantly higher than that of children in primary school (73.2%, 95% CI: 71.2%-74.6%). The GMC was negatively correlated with the time of inoculation (F = 32.17, P = 0.002). The mixture model enables a more comprehensive understanding of serological results by investigating four levels of antibody response, suggesting that there is a small fraction of the population with waning immunity. Children in kindergarten and primary school whom had received one dose of MMR vaccine were at a higher risk of mumps infection, particularly the 7-year-old group in the central region. Therefore, the single-dose MMR vaccine schedule has a limited impact on mumps control and prevention, and a two-dose MMR vaccine schedule should be introduced

Waning immunity of one-dose measles-mumps-rubella vaccine to mumps in children from kindergarten to early school age: a prospective study

Background: In China, one dose measles-mumps-rubella vaccine (MMR) was administered to children aged 18–24 months. The mumps incidence was still high. Data on the waning immunity to mumps after MMR vaccination are limited. This study aimed to describe the waning immunity to mumps in kindergarten and primary school children to provide a scientific basis for confirming an optimal age for a second dose. Methods: An observational, prospective study on one-dose MMR in children in kindergarten and primary school was conducted from 2015 to 2016. Waning immunity to mumps in terms of seropositivity and geometric antibody concentration (GMC) with time was analyzed. Results: In total, 7436 eligible subjects in kindergarten (3435) and primary school (4001) were included in 2015. The overall GMC (201.7 U/ml) and seropositivity (75.4%) to mumps antibodies in 2016 were significantly lower compared to those in 2015 (218.7 U/ml, 78.4%). Asymptomatic infection occurred within one year in 8.8% of children who received one-dose MMR. Conclusions: Children who received one-dose MMR in kindergarten and primary school were at high risk of mumps infection, and waning immunity occurred with time. Determining the optimal age for the second dose of MMR in children should be prioritized to prevent mumps epidemics