Recent discovery of the time reversal symmetry breaking magnetic Weyl semimetals (WSMs) has created a huge surge of activities in the field of quantum topological materials. In this work, we have ...studied systematically various magnetic orders, electronic structure and the interplay between the magnetic order and band topology in one such material, EuMg2Bi2 (EMB) and its Ca doped variant using first principle methods within the framework of density functional theory (DFT). Our thorough investigation reveals the existence of various magnetic order driven topological phases (for example, topological insulator in the A-type antiferromagnetic (A-AFM) phase with Eu moments aligned along the crystallographic a or b direction, Dirac semimetal in the A-AFM phase when Eu moments are parallel to c direction and Weyl semimetal in the ferromagnetic (FM) phase with Eu moments pointing along the c direction) in this material. These phases are found to be energetically very close and hence are expected to be tunable from one to the other by an external handle such as magnetic field or chemical substitution. Most importantly, we observe the existence of a single pair of Weyl points (WPs) connecting valence and conduction band very close to the Fermi level (FL) along Γ-A direction in the FM state of EuMg2Bi2 with Eu moments aligned along the c direction making it an ideal Weyl semimetal in its FM state exactly similar to EuCd2As2. On doping 50% and 67% Ca at Eu sites, we observe the single pair of WPs to move even closer to the FL which is highly desirable for application purposes. Further, we observe that the separation between the WPs in the pair decreases in doped compounds compared to that in the parent compound which has direct consequence on anomalous Hall conductivity (AHC). Our first principles calculation of AHC shows high peak values exactly at these WPs and the peak height decreases when we dope the system with Ca. Therefore, Ca doping can be a good external handle to tune AHC in this system.
•We observe AFM TI, Dirac semimetal and Weyl semimetal state in EuMg2Bi2.•Topological phases are magnetic order driven.•EuMg2Bi2 hosts a single pair of Weyl points in FMc state.•Ca doping at Eu site moves the Weyl points closer to Fermi level.•Ca doping can tune Anomalous Hall conductivity in EuMg2Bi2.
Networks have become increasingly important to model complex systems composed of interacting elements. Network data mining has a large number of applications in many disciplines including ...protein-protein interaction networks, social networks, transportation networks, and telecommunication networks. Different empirical studies have shown that it is possible to predict new relationships between elements attending to the topology of the network and the properties of its elements. The problem of predicting new relationships in networks is called link prediction. Link prediction aims to infer the behavior of the network link formation process by predicting missed or future relationships based on currently observed connections. It has become an attractive area of study since it allows us to predict how networks will evolve. In this survey, we will review the general-purpose techniques at the heart of the link prediction problem, which can be complemented by domain-specific heuristic methods in practice.
Microbial interactions shape the structure and function of microbial communities; microbial co-occurrence networks in specific environments have been widely developed to explore these complex ...systems, but their interconnection pattern across microbiomes in various environments at the global scale remains unexplored. Here, we have inferred an Earth microbial co-occurrence network from a communal catalog with 23,595 samples and 12,646 exact sequence variants from 14 environments in the Earth Microbiome Project dataset.
This non-random scale-free Earth microbial co-occurrence network consisted of 8 taxonomy distinct modules linked with different environments, which featured environment specific microbial co-occurrence relationships. Different topological features of subnetworks inferred from datasets trimmed into uniform size indicate distinct co-occurrence patterns in the microbiomes of various environments. The high number of specialist edges highlights that environmental specific co-occurrence relationships are essential features across microbiomes. The microbiomes of various environments were clustered into two groups, which were mainly bridged by the microbiomes of plant and animal surface. Acidobacteria Gp2 and Nisaea were identified as hubs in most of subnetworks. Negative edges proportions ranged from 1.9% in the soil subnetwork to 48.9% the non-saline surface subnetwork, suggesting various environments experience distinct intensities of competition or niche differentiation. Video abstract CONCLUSION: This investigation highlights the interconnection patterns across microbiomes in various environments and emphasizes the importance of understanding co-occurrence feature of microbiomes from a network perspective.
By using the first-principles electronic structure calculation, we have studied electronic band structures and topological properties of CsCl type binary superconductors RuTi and OsTi. Due to the ...protection of higher crystal symmetry, there are three-dimensional nodal rings around high symmetry points X, Y and Z without spin-orbital coupling (SOC). When SOC is considered, we find the topological phase transition from strong topological insulator phase in RuTi to Dirac semimetal in OsTi. The corresponding surface states are consistent with these nontrivial topologies. We also find strong topological insulator phases near Fermi level in isostructure material MgRh. Based on the topological surface states, the interface of heterostructure of superconductor RuTi (OsTi) and doped topological material MgRh could realize observable topological superconductivity. The nontrivial topological properties in binary superconductors RuTi and OsTi provide us new desirable avenues to study Majorana bound states in vortex cores of topological superconductor.
•We find topological phase transition from topological insulator phase in RuTi to semimetal in OsTi.•The strong topological insulator phases be found near Fermi level in isostructure material MgRh.•The corresponding surface states can be observed by an angle resolved photoemission spectroscopy.•The interface of heterostructure could realize observable topological superconductivity.
Resource minerals are necessary natural resources for developing renewable energy (RE) sources. The differing capabilities of various countries significantly impact the growth of RE. Minerals are ...used more intensively in producing RE than fossil fuel-based energy. Data from 30 provinces in China from 2000 to 2019 were used to determine the effects of mineral resource trade on RE development. We analyzed China's mineral trade network and topological properties using a complex network technique. Mineral trade patterns affect RE development and how technological advancements in RE mediate the impact on the dynamic econometric model. The energy mix should depend more on RE, and the reprocessing rate of minerals should be higher to demonstrate that RE capacity investments are made. Export strength and key influences benefit RE growth. Results concluded that the presence of other well-known elements that determine optimal resource use, such as increased renewable sector productivity and suboptimal substitution between the two energy sources, gently curved the extraction costs for mineral resources.
•Resource minerals are necessary natural resources for developing RE.•The differing capabilities of various countries significantly impact the growth of RE.•Mineral trade patterns affect RE development.•Export strength and trade integration benefit RE growth.
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Two-dimensional (2D) materials are at the forefront of current materials research due to their exciting and unique properties. 2D tellurides are emerging materials which are yet to be ...fully explored. To provide an overview of this emergent field, in this review, we discuss the structure, properties, synthesis methods, and applications of selected 2D tellurides, with stoichiometry of MxTey, and MxNyTez, (M, N are metal atoms). We present a summary of the latest advances in modeling, experimental synthesis, and characterization of 2D tellurides. Additionally, stress and strain-induced tunability of the physical properties have been reviewed, with a focus on the application of 2D tellurides in electronic, optoelectronic, and magnetic devices. We have discussed many emergent quantum properties of these materials. Finally, we conclude with a perspective on the future of 2D metal tellurides.
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Recently, graphene and other two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been widely explored due to their unique optical, mechanical, electrical and sensing ...properties for versatile electronic and optoelectronic applications. The atomically thin layers of TMDC materials have shown potential to replace state-of-the-art silicon-based technology. Graphene has already revealed an excess of new physics and multifaceted applications in several areas. Similarly, mono-layers of TMDCs such as molybdenum disulfide (MoS2) have also shown excellent electrical and optical properties possessing a direct band-gap of ∼1.8eV combined with high mechanical flexibility. In contrast to semi-metallic graphene, the semiconducting behavior of MoS2 allows it to overcome the deficiencies of zero-band-gap graphene. This review summarizes the synthesis of 2D MoS2 by several techniques, i.e., mechanical and chemical exfoliation, RF-sputtering, atomic layer deposition (ALD) and chemical vapor deposition (CVD), etc. Furthermore, extensive studies based on potential applications of MoS2 such as the sensor, solar cells, field emission and as an efficient catalyst for hydrogen generation has been included. Theoretical aspects combined with the experimental observations to provide more insights on the dielectric, optical and topological behavior of MoS2 was highlighted.
•Concepts of transport system vulnerability and resilience are defined and discussed.•Recent research on transport system vulnerability and resilience is reviewed.•Topological and system-based ...vulnerability studies are two distinct traditions.•Merits and drawbacks of these two traditions are discussed.•Cross-disciplinary collaboration helpful to exploit the potential of the research.
The transport system is critical to the welfare of modern societies. This article provides an overview of recent research on vulnerability and resilience of transport systems. Definitions of vulnerability and resilience are formulated and discussed together with related concepts. In the increasing and extensive literature of transport vulnerability studies, two distinct traditions are identified. One tradition with roots in graph theory studies the vulnerability of transport networks based on their topological properties. The other tradition also represents the demand and supply side of the transport systems to allow for a more complete assessment of the consequences of disruptions or disasters for the users and society. The merits and drawbacks of the approaches are discussed. The concept of resilience offers a broader socio-technical perspective on the transport system’s capacity to maintain or quickly recover its function after a disruption or a disaster. The transport resilience literature is less abundant, especially concerning the post-disaster phases of response and recovery. The research on transport system vulnerability and resilience is now a mature field with a developed methodology and a large amount of research findings with large potential practical usefulness. The authors argue that more cross-disciplinary collaborations between authorities, operators and researchers would be desirable to transform this knowledge into practical strategies to strengthen the resilience of the transport system.
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