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Since the discovery of intrinsic ferromagnetism in atomically thin Cr2Gr2Te6 and CrI3 in 2017, research on two-dimensional (2D) magnetic materials has become a highlighted topic. Based on 2D magnetic materials and their heterostructures, exotic physical phenomena at the atomically thin limit have been discovered, such as the quantum anomalous Hall effect, magneto-electric multiferroics, and magnon valleytronics. Furthermore, magnetism in these ultrathin magnets can be effectively controlled by external perturbations, such as electric field, strain, doping, chemical functionalization, and stacking engineering. These attributes make 2D magnets ideal platforms for fundamental research and promising candidates for various spintronic applications. This review aims at providing an overview of the structures, properties, and external controls of 2D magnets, as well as the challenges and potential opportunities in this field.

Achieving high tunneling magnetoresistance (TMR) in molecular-scale junctions is attractive for their applications in spintronics. By using density-functional theory (DFT) in combination with the nonequilibrium Green's function (NEGF) method, we investigated the spin-resolved charge transport properties of molecular junctions based on Co-Salophene symmetric/asymmetric dimers. We found that nearly 100% spin-injection efficiency (SIE) can be achieved in parallel spin configuration with the spin dependent quantum interference effect. In particular, the high TMR is demonstrated to be closely related to the molecular symmetry, reaching 4600% and 2200% for a symmetric and asymmetric molecular junction (MJ), respectively. Further inelastic transport analyses reveal that the excellent TMR properties of the symmetric MJ can still be preserved in the electron-vibration interaction and temperature effects being considered, which provides an insight for designing future molecular integrated circuit devices.

Recently, novel two-dimensional (2D) magnetic materials have drawn enormous research attention due to their interesting tunable electronic and magnetic properties. However, 2D Janus materials with intrinsic magnetism are rare. We investigate the geometric and electronic properties of monolayer (ML) and bilayer (BL) intrinsic magnetic Janus Cr2Cl3I3 using first-principles calculations. We find that ML Janus Cr2Cl3I3 is a magnetic semiconductor with the band gaps for the spin-α and spin-β channels being 2.11 and 3.83 eV, respectively. The magnetic ground state of ML Cr2Cl3I3 can be effectively modulated by biaxial strain from the ferromagnetic (FM) state to the antiferromagnetic (AFM) state. Meanwhile, ML Cr2Cl3I3 experiences an electronic phase transition from a half semiconductor (HSC) to a bipolar magnetic semiconducor (BMS) and finally a spin-unpolarized semiconductor with increasing strain. More interestingly, as the biaxial strain increases, the Curie temperature for the FM ground state increases from 36.3 K to 49.2 K. As for bilayer (BL) Cr2Cl3I3, the stacking order could effectively affect the magnetic and electronic properties. The most stable stacking order is AB-II type, followed by AA-II, AB-ClI, AA-ClI, AB-ClCl and AA-ClCl stacking orders. They are all spin-polarized BMS. The magnetic and electronic properties of BL Cr2Cl3I3 change with different stacking orders, possibly due to the quantum confinement effect and interlayer interactions. The stability of ML Cr2Cl3I3 is confirmed by the phonon spectrum and molecular dynamics simulations. The tunable electronic properties together with intrinsic ferromagnetism enrich the diversity of Janus 2D Cr2Cl3I3, which has potential applications in spintronic devices.

Phonon hydrodynamics, a collective motion of phonons, has recently attracted renewed attention since its temperature window has been greatly extended in layered materials. The exploration of phonon hydrodynamics bears importance in understanding phonon collective behavior, and its window is crucial for determining the phonon transport regime and engineering the heat transport. Thus, strategies for continuous tuning of the hydrodynamic window are needed, but it remains a challenge. In this work, we demonstrate that the phonon hydrodynamic window in bilayer graphene can be strongly altered by the strain based on theoretical calculations. In particular, the phonon hydrodynamics can be observed at 60 K in unstrained bilayer graphene, while only 0.25% strain can reduce this temperature to 28 K. This strong strain dependence not only provides an efficient way of modulating the phonon collective behavior but also renders a possibility of strain-induced transition of phonon transport regime.

The realization of high-temperature excitonic Bose-Einstein condensation (BEC) in practical materials poses great challenges, because of strict constraints in symmetry, exciton binding, lifetime, and interaction. Here, using first-principles methods and symmetry analysis, we propose a new route to realize high-temperature excitonic BEC in centrosymmetric 2D materials, exploiting the parity symmetry of band edges and reduced Coulomb screening. We demonstrate it by taking monolayer TiS3 as an example, whose lowest-energy exciton shows small exciton mass, small Bohr radius, large binding, and long lifetime simultaneously. The phase diagram of electron-hole systems is further constructed, showing that both BEC and superfluidity can be realized at high temperature and in a broad range of exciton density. Importantly, we reveal that the high-temperature character of excitonic BEC is robust against thickness, beneficial for its experimental observation. By application of this general strategy to 2D materials in the database, monolayer AuBr and BiS2 are identified as promising candidates for high-temperature excitonic BEC.

Ultrathin and lightweight MoS2/carbon nanotube (CNT) interlayers are developed to effectively trap polysulfides in high-performance lithium–sulfur (Li–S) batteries. The MoS2/CNT interlayer is constructed by loading MoS2 nanosheets onto a cross-stacked CNT film. The CNT film with excellent conductivity and superior mechanical properties provides the Li–S batteries with a uniform conductive network, a supporting skeleton for the MoS2 nanosheets, as well as a physical barrier for the polysulfides. Moreover, chemical interactions and bonding between the MoS2 nanosheets and the polysulfides are evident. The electrode with the MoS2/CNT interlayer delivers an attractive specific capacity of 784 mA h g−1 at a high capacity rate of 10 C. In addition, the electrode demonstrates a high initial capacity of 1237 mA h g−1 and a capacity fade as low as −0.061% per cycle over 500 charge/discharge cycles at 0.2 C. The problem of self-discharge can also be suppressed with the introduction of the MoS2/CNT interlayer. The simple fabrication procedure, which is suitable for commercialization, and the outstanding electrochemical performance of the cells with the MoS2/CNT interlayer demonstrate a great potential for the development of high-performance Li–S batteries.

The structural or electronic symmetry breaking of the host lattice is a recurrent phenomenon in many quantum materials, including superconductors. Yet, how these broken symmetry states affect the electronic pair wave function of superconductivity have been rarely elucidated. Here, using low-temperature scanning tunneling microscopy and first-principles calculations, we identify the broken rotational symmetry via stripe ordering on the (001) surface of perovskite BaBi3 films grown by molecular beam epitaxy, and show that it consequently leads to anisotropic superconductivity with twofold symmetry. In contrast, the structural disorder smears out the anisotropy of electron pairing and fills superconducting subgap density of states as the film thickness is reduced. A quasi-long range model of superconducting fluctuations is revealed to describe the tunneling conductance spectra of thin BaBi3 films well, and to exemplify how disorders contribute to the low-energy quasiparticle excitations in superconductors. Our findings help understand the effects of symmetry breaking states and disorders on superconductivity, particularly the existing tunneling conductance spectra there., 38 pages, 15 figures

Giardia duodenalis is a common protozoan that colonizes and reproduces in the small intestine, causing giardiasis. This parasite infects a wide range of vertebrate hosts, including humans, domestic animals and wildlife. It has been suggested that chinchillas (Chinchilla lanigera) kept as domestic pets are potential reservoirs for the zoonotic transmission of G. duodenalis. In this study, 140 chinchilla samples from four cities in China were examined to determine the prevalence of G. duodenalis. Thirty-eight (27.1%) chinchillas were found to be positive for G. duodenalis. The prevalence of infection was analyzed in relation to collection site, age and sex. Molecular characterization was also carried out on the 38 chinchilla samples to determine common genotypes. G. duodenalis assemblages A and B were identified in the chinchilla samples by analysis of the small subunit ribosomal RNA (ssur RNA) gene. Genotyping at the subtype level using multiple genes (glutamate dehydrogenase (gdh), triose phosphate isomerase (tpi) and β-giardin (bg) genes) determined that the majority of assemblage A isolate sequences were identical to subtype AI. Assemblage B isolates showed variability among the nucleotide sequences belonging to subtype BIV. This is the first report of G. duodenalis in chinchillas from China. As subtype AI and BIV are associated with human infection, G. duodenalis in chinchillas should be regarded as zoonotic.

Among the known transition metal dichalcogenides, monolayer ${\mathrm{VS}}_{2}$ has attracted particular attention because of its intrinsic ferromagnetism and great application potential as a high-performance functional nanomaterial. Here, using first-principles calculations, we study the structural and electronic phase transitions in monolayer ${\mathrm{VS}}_{2}$ induced by charge doping. We show that without electron or hole doping, ${\mathrm{VS}}_{2}$ stabilizes in the 2H phase and is a bipolar magnetic semiconductor (BMS) whose valence and conduction states near the Fermi level carry opposite spin polarization. With the increase of hole doping concentration, ${\mathrm{VS}}_{2}$ will first experience an electronic phase transition from a BMS to a half metal, followed by a 2H-to-1T structural phase transition (SPT) which concomitantly results in another electronic phase transition from the half metal to a normal metal. Moreover, the reduced reaction barrier from the 2H to 1T phases by hole doping can make the occurrence of the SPT easier. However, electron doping can only induce the BMS-to-half metal electronic phase transition but will not trigger the SPT within the experimentally accessible doping regime. The different effects of hole and electron dopings on the SPT are further explained by the energy band diagram of ${\mathrm{VS}}_{2}$. These results establish the potential for ${\mathrm{VS}}_{2}$ utilization in innovative phase-change electronic and spintronic devices.

Migration of oxygen vacancies has been proposed to play an important role in the bipolar memristive behaviors since oxygen vacancies can directly determine the local conductivity in many systems. However, a recent theoretical work demonstrated that both migration of oxygen vacancies and coexistence of cation and anion vacancies are crucial to the occurrence of bipolar memristive switching, normally observed in the small-sized NiO. So far, experimental work addressing this issue is still lacking. In this work, with conductive atomic force microscope and combined scanning transmission electron microscopy & electron energy loss spectroscopy, we reveal that concentration surplus of Ni vacancy over O vacancy determines the bipolar memristive switching of NiO films. Our work supports the dual-defects-based model, which is of fundamental importance for understanding the memristor mechanisms beyond the well-established oxygen-vacancy-based model. Moreover, this work provides a methodology to investigate the effect of dual defects on memristive behaviors., ACS Applied Materials & Interfaces 2016

Background Enterocytozoon bieneusi is the most frequently diagnosed microsporidian species in humans and a wide range of animals. This study was conducted to assess the prevalence and molecular characteristics of E. bieneusi in dairy cattle in Henan Province of central China and the Ningxia Hui Autonomous Region of northwest China. Findings Of 879 fresh fecal specimens, 24.3 % (214/879) tested positive for E. bieneusi by nested polymerase chain reaction (PCR) based on the internal transcriber spacer (ITS) gene. The highest infection rate, 46.8 % (51/109, P

A multifunctional interlayer, composed of molybdenum diphosphide (MoP2 ) nanoparticles and a carbon nanotube (CNT) film, is introduced into a lithium-sulfur (Li-S) battery system to suppress polysulfide migration. Molybdenum diphosphide acts as the catalyst and can capture polysulfides and improve the polysulfide conversion activity during the discharge/charge processes. The CNT film acts as a conductive skeleton to support the MoP2 nanoparticles and to ensure their uniform distribution. The CNT film physically hinders polysulfide migration, acts as a current collector, and provides abundant electron pathways. The Li-S battery containing the multifunctional MoP2 /CNT interlayer exhibits excellent electrochemical performance. It delivers a reversible specific capacity of 905 mA h g-1 over 100 cycles at 0.2 C, with a capacity decay of 0.152% per cycle. These results suggest the introduction of the multifunctional CNT/MoP2 interlayer as an effective and practical method for producing high-performance Li-S batteries.

We theoretically investigate the electronic properties of the interface between quantum spin Hall (QSH) and quantum anomalous Hall (QAH) insulators. A robust chiral gapless state, which substantially differs from edge states of QSH or QAH insulators, is predicted at the QSH/QAH interface using an effective Hamiltonian model. We systematically reveal distinctive properties of interface states between QSH and single-valley QAH, multivalley high-Chern-number QAH and valley-polarized QAH insulators based on tight-binding models using the interface Green's function method. As an example, first-principles calculations are conducted for the interface states between fully and semihydrogenated bismuth (111) thin films, verifying the existence of interface states in realistic material systems. Due to the physically protected junction structure, the interface state is expected to be more stable and insensitive than topological boundary states against edge defects and chemical decoration. Hence our results of the interface states provide a promising route towards enhancing the performance and stability of low-dissipation electronics in real environment.

Cryptosporidium and Enterocytozoon bieneusi are the most prevalent protist pathogens responsible for inducing human and animal diseases worldwide. The aim of the present work was to determine the occurrence of Cryptosporidium spp. and E. bieneusi in pet chinchillas in China. One hundred forty fecal samples were collected from four cities: Beijing, Zhengzhou, Anyang and Guiyang. They were then examined with PCR amplification of the small subunit ribosomal RNA (SSU rRNA) of Cryptosporidium spp. and the internal transcribed spacer (ITS) of the ribosomal RNA of E. bieneusi. The infection rates for Cryptosporidium spp. and E. bieneusi were 10.0% and 3.6%, respectively. Sequence analysis of SSU rRNA gene products identified two Cryptosporidium spp., Cryptosporidium ubiquitum (n=13) and Cryptosporidium parvum (n=1). Subtyping with the 60-kDa glycoprotein (gp60) gene showed that all C. ubiquitum isolates belonged to zoonotic subtype family XIId, while the subtype of the C. parvum isolate could not be identified. Two E. bieneusi genotypes were identified in five samples, zoonotic genotypes BEB6 (n=3) and D (n=2). This is the first report of C. ubiquitum and C. parvum, and E. bieneusi in chinchillas. This result indicates that pet chinchillas may be a potential source of human infection with Cryptosporidium spp. and E. bieneusi.

Resistive switching effect in conductor/insulator/conductor thin-film stacks is promising for resistance random access memory with high-density, fast speed, low power dissipation and high endurance, as well as novel computer logic architectures. NiO is a model system for the resistive switching effect and the formation/rupture of Ni nanofilaments is considered to be essential. However, it is not clear how the nanofilaments evolve in the switching process. Moreover, since Ni nanofilaments should be ferromagnetic, it provides an opportunity to explore the electromagnetic coupling in this system. Here, we report a direct observation of Ni nanofilaments and their specific evolution process for the first time by a combination of various measurements and theoretical calculations. We found that multi-nanofilaments are involved in the low resistance state and the nanofilaments become thin and rupture separately in the RESET process with subsequent increase of the rupture gaps. Theoretical calculations reveal the role of oxygen vacancy amount in the evolution of Ni nanofilaments. We also demonstrate electromagnetic coupling in this system, which opens a new avenue for multifunctional devices.

We investigated the generation of spherical continuous-tilings of the chaotic attractors or the filled-in Julia sets from the plane mappings. We build three plane mappings, which can be used to construct the continuous patterns on the surfaces of the hexahedron and the unit sphere. We discuss the coordinate transformation for a spatial point between the different coordinate systems and further discuss how to project a spherical point onto a surface of the inscribed hexahedron. We present a method of constructing a spherical pattern with the pattern of a square on the inscribed hexahedron from an arbitrary projective angle, and generate spherical patterns from the three plane mappings. The results show that we can construct a great number of spherical patterns of the chaotic attractors and the filled-in Julia sets from the plane mappings, which are based on the square lattice and meet the requirements of the continuity and the four rotation symmetries on the lattice's boundaries.

Background Cryptosporidium spp. are zoonotic parasites responsible for diarrhoeal diseases in animals and humans worldwide. Cattle are the most common mammalian species in which Cryptosporidium is detected, with pre-weaned calves considered to be reservoirs for zoonotic C. parvum. In October 2013, severe diarrhoea was observed in 396 pre-weaned calves at a farm in the Ningxia Autonomous Region of Northwestern China. 356 of the infected calves died despite antibiotic therapy. Findings 252 faecal samples were collected from the investigated farm. The identity of Cryptosporidium species was determined by polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP) analysis, and by DNA sequence analysis of the small subunit (SSU) rRNA gene. C. parvum was subtyped using sequence analysis of the 60 kDa glycoprotein (gp60) gene. The highest infection rate of 83.3% (40/48) was seen in 2–3-week-old calves with diarrhoea, corresponding to the age at which animals died. Three Cryptosporidium species were identified, including C. parvum (n = 51), C. bovis (n = 1), and C. ryanae (n = 1). All C. parvum isolates were further identified as subtype IIdA15G1. Conclusions Cryptosporidium parvum was likely to be most responsible for diarrhoea and death. This is the first report of a cryptosporidiosis outbreak caused by C. parvum IIdA15G1 in Chinese dairy cattle.