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Superconductor-ferromagnet interfaces in two-dimensional heterostructures present a unique opportunity to study the interplay between superconductivity and ferromagnetism. The realization of such nanoscale heterostructures in van der Waals (vdW) crystals remains largely unexplored due to the challenge of making atomically-sharp interfaces from their layered structures. Here, we build a vdW ferromagnetic Josephson junction (JJ) by inserting a few-layer ferromagnetic insulator Cr2Ge2Te6 into two layers of superconductor NbSe2. The critical current and corresponding junction resistance exhibit a hysteretic and oscillatory behavior against in-plane magnetic fields, manifesting itself as a strong Josephson coupling state. Also, we observe a central minimum of critical current in some JJ devices as well as a nontrivial phase shift in SQUID structures, evidencing the coexistence of 0 and π phase in the junction region. Our study paves the way to exploring sensitive probes of weak magnetism and multifunctional building-blocks for phase-related superconducting circuits using vdW heterostructures., The superconductor-ferromagnet interface provides a unique opportunity to study the interplay between superconductivity and ferromagnetism. Here, the authors build a van der Waals ferromagnetic Josephson junction evidencing a strong 0 and π phase Josephson coupling.

The interplay between quenched disorder and critical behavior in quantum phase transitions is conceptually fascinating and of fundamental importance for understanding phase transitions. However, it is still unclear whether or not the quenched disorder influences the universality class of quantum phase transitions. More crucially, the absence of superconducting-metal transitions under in-plane magnetic fields in 2D superconductors imposes constraints on the universality of quantum criticality. Here, we observe the thickness-tuned universality class of superconductor-metal transition by changing the disorder strength in β - W films with varying thickness. The finite-size scaling uncovers the switch of universality class: quantum Griffiths singularity to multiple quantum criticality at a critical thickness of t c ⊥ 1 ~ 8 n m and then from multiple quantum criticality to single criticality at t c ⊥ 2 ~ 16 n m . Moreover, the superconducting-metal transition is observed for the first time under in-plane magnetic fields and the universality class is changed at t c ‖ ~ 8 n m . The observation of thickness-tuned universality class under both out-of-plane and in-plane magnetic fields provides broad information for the disorder effect on superconducting-metal transitions and quantum criticality.

Stimulated by novel properties in topological insulators, experimentally realizing quantum phases of matter and employing control over their properties have become a central goal in condensed matte...

We experimentally demonstrated an optical controlled terahertz modulator based on the 3D Dirac semimetal Cd3As2 thin film (~100 nm, λ/3000). Utilizing the time-resolved terahertz spectroscopy, the photoactive characters of Cd3As2 thin film are investigated. The measurements reveal that Cd3As2 modulator exhibits a low optical threshold (< 63.5 μJ/cm2) and ultrafast (< 20 ps) broadband (0.2-1.5 THz) modulation of terahertz waves. Moreover, integrated with the metamaterials structures, Cd3As2 could potentially be used as photo-sensitive and ultrafast reconfigurable terahertz resonant plasmonic/meta-device.

The thermoelectric effects of topological semimetals have attracted tremendous research interest because many topological semimetals are excellent thermoelectric materials and thermoelectricity serves as one of their most important potential applications. In this work, we reveal the transient photothermoelectric response of Dirac semimetallic Cd

In this work, we use optical pump-terahertz (THz) probe spectroscopy to investigated the impurity-induced topological phase transition and the photo-induced carrier behavior in cadmium arsenide (Cd3As2), a three-dimensional Dirac semimetal. By comparing the dynamics of different temperature and pump fluence, we discuss the carrier dynamics and physical mechanism caused by impurity.

Photoelectric detection technology is extremely significant on account of its extensive applications in commercial and military fields, but high-performance array photodetectors based on Dirac semimetal thin film materials are rarely reported. Hence, we demonstrate photodetectors based on a three dimensional (3D) topological Dirac semimetal (DSM) (Cd1−xZnx)3As2/MoO3 array heterojunction, showing ultrahigh photoresponsivity, detectivity and external quantum efficiency in the ultra-broadband spectrum (405–4500 nm) of 3.1 A W−1, 6.4 × 1010 Jones and 855.8%, respectively, meanwhile possessing array unit performance repeatability and excellent time stability under atmospheric conditions at room temperature. The device exhibits an incredible current reversal phenomenon under the action of both light illumination and temperature variation elements, which can be attributed to a thermoelectromotive force effect. These excellent photoelectric properties illustrate that the fabrication of the 3D DSMs/inorganic thin film heterojunction is a suitable method for preparing distinguished infrared array photodetectors in the field of infrared telecommunications and scanning imaging.

Mechanically exfoliated two-dimensional ferromagnetic materials (2D FMs) possess long-range ferromagnetic order and topologically nontrivial skyrmions in few layers. However, because of the dimensionality effect, such few-layer systems usually exhibit much lower Curie temperature (TC) compared to their bulk counterparts. It is therefore of great interest to explore effective approaches to enhance their TC, particularly in wafer-scale for practical applications. Here, we report an interfacial proximity-induced high-TC 2D FM Fe3GeTe2 (FGT) via A-type antiferromagnetic material CrSb (CS) which strongly couples to FGT. A superlattice structure of (FGT/CS)n, where n stands for the period of FGT/CS heterostructure, has been successfully produced with sharp interfaces by molecular-beam epitaxy on 2-inch wafers. By performing elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally discovered that TC of 4-layer Fe3GeTe2 can be significantly enhanced from 140 K to 230 K because of the interfacial ferromagnetic coupling. Meanwhile, an inverse proximity effect occurs in the FGT/CS interface, driving the interfacial antiferromagnetic CrSb into a ferrimagnetic state as evidenced by double-switching behavior in hysteresis loops and the XMCD spectra. Density functional theory calculations show that the Fe-Te/Cr-Sb interface is strongly FM coupled and doping of the spin-polarized electrons by the interfacial Cr layer gives rise to the TC enhancement of the Fe3GeTe2 films, in accordance with our XMCD measurements. Strikingly, by introducing rich Fe in a 4-layer FGT/CS superlattice, TC can be further enhanced to near room temperature. Our results provide a feasible approach for enhancing the magnetic order of few-layer 2D FMs in wafer-scale and render opportunities for realizing realistic ultra-thin spintronic devices., Utilizing proximity effect, we realize an effective and reliable approach to accomplish near-room-temperature (286.7 K) ferromagnetic order and double switching behavior in wafer-scale 4-layer-Fe3GeTe2/1.6-nm-CrSb superlattice.

The carbonate–CO2–H2O interaction in a closed system under burial conditions was simulated in diamond anvil cell (DAC) with an in situ Raman spectroscopy. Experiments were performed in $${\text{H}}_{2} {\text{CO}}_{3}$$ solution at acidic pH (≈ 5.6), 20–260 °C, and atmospheric pressure to about 400 MPa. Pressure was first solely increased to separately evaluate the pressure effect on carbonate dissolution/precipitation. Then temperature and pressure were increased together alike in the burial process, to monitor the dissolution/precipitation tendency of carbonate during burial. A continuous dissolution was observed for both limestone and dolostone when solely increasing pressure. A rapid dissolution and then continuous precipitation were observed when increasing temperatures and pressures simultaneously. These observations indicate that pressure has a positive effect (prograde solubility), while temperature has a negative effect (retrograde solubility) on CO2 solubility and carbonate dissolution. In case of low initial CO2 content as our experiments revealed, the increase in solid carbonate volume and a counterbalance decrease in porosity caused merely by increasing burial depth are minor (

Two-dimensional (2D) ferromagnetic materials have been discovered with tunable magnetism and orbital-driven nodal-line features. Controlling the 2D magnetism in exfoliated nanoflakes via electric/magnetic fields enables a boosted Curie temperature (TC) or phase transitions. One of the challenges, however, is the realization of high TC 2D magnets that are tunable, robust and suitable for large scale fabrication. Here, we report molecular-beam epitaxy growth of wafer-scale Fe3+XGeTe2 films with TC above room temperature. By controlling the Fe composition in Fe3+XGeTe2, a continuously modulated TC in a broad range of 185–320 K has been achieved. This widely tunable TC is attributed to the doped interlayer Fe that provides a 40% enhancement around the optimal composition X = 2. We further fabricated magnetic tunneling junction device arrays that exhibit clear tunneling signals. Our results show an effective and reliable approach, i.e. element doping, to producing robust and tunable ferromagnetism beyond room temperature in a large-scale 2D Fe3+XGeTe2 fashion.

The motion of Abrikosov vortices is the dominant origin of dissipation in type II superconductors subjected to a magnetic field, which leads to a finite electrical resistance. It is generally believed that the increase in the magnetic field results in the aggravation of energy dissipation through the increase in vortex density. Here, we show a distinctive re-entrance of the dissipationless state in quasi-one-dimensional superconducting Ta

Stimulated by novel properties in topological insulators, experimentally realizing quantum phases of matter and employing control over their properties have become a central goal in condensed matter physics. β-silver telluride (Ag

A conventional passive matching method cannot be used for a low-frequency ultrawideband (UWB) antenna of high performance. In this paper, an amplifier module is combined with a short monopole antenna to design a high-performance active receiving antenna for 10 kHz–100 MHz UWB through model simulation. In addition, theoretical analysis of the antenna’s noise is made, and the theoretical basis for improving the sensitivity of the active antenna is obtained. Finally, the amplifier module is fabricated and the sensitivity of the antenna is tested using the equivalent capacitance substitution method. Tests show that the active antenna has very high sensitivity, bandwidth, and gain, and can be applied to cosmic radio signal detection.

We have for the first time demonstrated a SESAM-like device operating beyond 3 micron. The SESAM-like device is comprised of a highly-reflective Si/SiO Bragg reflector, a Dirac semimetal thin film absorber and a mica substrate as the passivation layer.

We have for the first time reported third harmonic generation in a three-dimensional Dirac semimetal Cd3As2 film. We further demonstrate that a simple planar cavity can be used to significantly enhance the nonlinear response.

In this Letter, we successfully introduce a long-lived non-radiative photocarrier decay component in a Dirac semimetal Cd

Recently, discovery of three-dimensional (3D) topological Dirac/Weyl semi-metal opens up a new frontier fields for neoteric type of photodetectors. As a most representative 3D Dirac semi-metal, Cadmium arsenide (Cd3As2) has ultra-high charge mobility beyond graphene and possess strong light and matter interaction. Herein, photodetector prototype based on micro-nanometer scaled Cd3As2 was developed, which has high photocurrent response even under slight bias of 1 mV and its responsivity could be up to 4.65 A/W at near infrared waveband of 808 nm. Moreover, the Cd3As2/CuPc heterojunction was further introduced for suppress dark current of Dirac semimetal Cd3A2 nanobelt that would effectively improve photoelectric detection performance. As expected, the responsivity (R) of Cd3As2/CuPc has been significantly enhanced in visible (405 nm) to near-infrared (980 nm) region, and maximum R and optimal detectivity (D*) of detector can be reach about 142.5 A/W and 7.83 × 1010 Jones under irradiation of 808 nm laser, respectively. All of the results indicate that 3D Dirac semi-metal Cd3As2 and its heterojunction design are great prospect applied in high-performance broadband detection devices.

Cadmium arsenide (Cd3As2), an emerging three-dimensional Dirac semimetal, has recently generated significant interest in the area of ultrafast optics and optoelectronics. However, its nonlinear susceptibility has not been experimentally studied; thus, it is not yet possible to evaluate its potential in nonlinear optics. In this work, we investigate third harmonic generation (THG) in a 100 nm thick Cd3As2 film using broadband infrared femtosecond lasers (across 1500–2350 nm). The χ3 of Cd3As2 (2.30 × 10−19 m2 V−2) is obtained by comparing the THG spectra with a glass substrate, graphene, and monolayer MoS2. We further demonstrate a simple approach to enhance the THG signal by introducing an underlying planar micro-cavity. An enhancement of about 420 times in the THG signal was recorded at ≃1560 nm. Our results indicate that Cd3As2 thin films can provide a similar platform for nonlinear optics with respect to graphene and may offer unique potential in the mid-infrared due to its broadband light–matter interaction and excellent tunability.

The purpose of this study was to investigate the epidemiological characteristics of carbapenem-resistant Klebsiella pneumoniae (CRKP) in Shanghai Children’s Hospital in China. Twenty-two non-duplicate CRKP strains were collected from pediatric patients between March and June in 2014. Antimicrobial susceptibility testing was conducted by the agar dilution method. Beta-lactamases were characterized by polymerase chain reaction (PCR) and DNA sequencing. The transferability of bla NDM-1 was investigated by conjugation experiment. The plasmids bearing antibiotic resistance genes were characterized by S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and Southern hybridization. Clonal relatedness was evaluated by PFGE and multilocus sequence typing (MLST). The clinical data of patients were retrospectively reviewed. The 22 CRKP strains were resistant to most of the antimicrobial agents tested, except tigecycline and colistin. Overall, 59, 77, and 100 % of these strains were resistant to imipenem, meropenem, and ertapenem, respectively. The bla NDM-1 was positive in 77.3 % (17/22) of the CRKP strains, of which the 16 isolates from inpatients were designated as ST37 (n = 9) and ST76 (n =7) and one isolate from an outpatient belonged to ST846. The 17 bla NDM-1-positive isolates belonged to PFGE type A (n = 9), type C (n = 7), or type B (n = 1). The plasmids bearing bla NDM-1 could be transferred into recipient Escherichia coli J53 through conjugation in 88.2 % (15/17) of the strains. The hybridization results showed that the plasmids carrying the bla NDM-1 gene were approximately 50–240 kb in size. This is the first report of an outbreak caused by NDM-1-producing K. pneumoniae ST76 and ST37 among neonates.

In this Letter, we successfully introduce a long-lived non-radiative photocarrier decay component in a Dirac semimetal Cd3As2 thin film via Mn doping. The long-lived decay component is found to vary between 200 ps and 2.8 ns with different Mn concentrations and probing wavelengths. Most remarkably, the elongated transients persist over the important mid-infrared wavelengths (observed up to 4 μm). Saturable absorption measurement reveals stronger modulation effects for long-width pulses (∼80 ps) from the Mn-doped samples. Our results provide new insights into the effect of transition-metal doping on the ultrafast optical properties of Dirac semimetal Cd3As2 and establish Cd3As2 as a highly amendable material for mid-infrared photonic applications.

By employing optical pump Terahertz (THz) probe spectroscopy, a three dimensional (3D) Dirac semimetal, Cd3As2 film, was investigated systematically at room temperature. After photoexcitation at 400/800 nm, the rise time of photoenhanced THz photoconductivity (PC) is about ∼1.0 ps, increasing slightly with the pump fluence, in which time scale, photoexcited electrons and holes establish separate Fermi distribution with electrons in the conduction band and holes in the valence band via fast carrier-carrier scattering and carrier-phonon coupling. The subsequent THz PC relaxation shows single exponential decay with a time constant of ∼6.0 ps that is independent of pump fluence. The relaxation process is dominated by the electron-hole recombination via a radiative and nonradiative way, which is mediated by the phonon-phonon scattering. The optically induced THz complex PC can be well fitted with the Drude-Smith model. Our experimental results shed light on understanding the photocarrier dynamics of the 3D Dirac semimetal materials at THz frequency.

Based on well correlation, division of sedimentary facies and microfacies, core observation, and analysis of rock thin sections, the authors comparatively analyzed the sedimentation and diagenesis of the oolitic beaches in the Puguang and Yuanba areas of northeastern Sichuan Basin, and expounded their control on reservoirs. In the Puguang area the oolitic beach is thick and lateral migration distance is short, intervals overlaid one another, while in the Yuanba area the oolitic beach is thin and lateral migration distance is long. The two areas both experienced various types of diagenesis. There happened intense early dissolution and wide-spread dolomitization in the oolitic beach of the Puguang area, where type-I reservoirs of high porosity and permeability are developed. In the Yuanba area, strong compaction and pressure dissolution, and late burial cementation led to the development of type-III reservoirs of low porosity and permeability. The main factors that control the sedimentation and diagenesis are paleotopography and changes in sea level. Sedimentation controls the distribution and thickness of reservoir, and diagenesis determines the porosity formation and evolution and ultimately the reservoir quality. Key words: northeastern Sichuan, Feixianguan Formation, oolitic beach, sedimentation, diagenesis

In this Letter, we demonstrate an electrically contacted saturable absorber (SA) device based on topological Dirac semimetal Cd3As2. With a current-induced temperature change in the range of 297–336 K, the modulation depth of the device is found to be significantly altered from 33% to 76% (under the irradiation of a 1560 nm femtosecond laser). The broad tuning of the modulation depth is attributed to the strong temperature dependence of the carrier concentration close to room temperature. The simple tuning mechanism uncovered here, together with the compatibility with III-V compounds substrate, such as GaAs, points to the potential of fabricating broadband, electrically tunable, SESAM-like devices based on emerging bulk Dirac materials.

The Helfand's lattice theory of polymer interface has been extended to deal with the interface between thermotropic small molecular liquid crystals and flexible polymers. The main findings of the theoretical calculations are: (1) the interface of flexible polymer and the ordered nematic liquid crystal is very narrow due to the fact that the ordered nematic phase excludes strongly the flexible polymer segments; (2) the interfacial tension and the anisotropic factors of polymer bonds posses a first order transition, when the liquid crystal-rich phase undergoes the isotropic to nematic phase transition, which is characterized mainly by the fact that polymer bonds prefer to return back to the saturated polymer solution phase by reducing the probability of stretching into the liquid crystalline phase.

We investigated the magneto-optical Kerr effects in C2v symmetric Fe/GaAs(110) film and quantitatively separated the linear and quadratic Kerr contributions with the rotating field method. The linear Kerr effect was experimentally found to have twofold anisotropy with crystal orientation, in well agreement with the theoretical prediction. In addition, the quadratic Kerr effects exhibit both twofold and fourfold anisotropy. The calculation based on a 4 × 4 transfer matrix method indicates that the anisotropies of the linear and quadratic Kerr effects both originate from the second order magneto-optical coupling. The C2v symmetric film with anisotropic linear Kerr effect may have a potential application on the future precise magneto-optical sensors.

Proteins encoded by a 9.5-kb DNA segment, termed the region of difference (RD), of Mycobacterium tuberculosis have been demonstrated to be important in bacterial virulence, vaccine development and the design of diagnostic reagents. This study evaluated the immunogenic properties of Rv3425, a member of the PPE family of proteins, encoded by an open reading frame found in RD11 of M. tuberculosis, in comparison with two other well-known antigens, the early secreted antigen target 6 (ESAT-6) and the 10-kDa culture filtrate protein (CFP-10). RT-PCR demonstrated that Rv3425 mRNA is expressed in liquid culture by M. tuberculosis H37Rv. When tested in a conventional ELISA in the form of a His-tagged recombinant protein, Rv3425 revealed a statistically significant antigenic distinction between healthy bacille Calmette–Guérin (BCG)-vaccinated controls and tuberculosis (TB) patients (p

The magnetic and microwave absorption properties of the interstitial atom modified intermetallic compound Ce2Fe17NX have been investigated. The Ce2Fe17NX compound shows a planar anisotropy with saturation magnetization of 1088 kA/m at room temperature. The Ce2Fe17NX paraffin composite with a mass ratio of 1:1 exhibits a permeability of μ′ = 2.7 at low frequency, together with a reflection loss of −26 dB at 6.9 GHz with a thickness of 1.5 mm and −60 dB at 2.2 GHz with a thickness of 4.0 mm. It was found that this composite increases the Snoek limit and exhibits both high working frequency and permeability due to its high saturation magnetization and high ratio of the c-axis anisotropy field to the basal plane anisotropy field. Hence, it is possible that this composite can be used as a high-performance thin layer microwave absorber.

A special kind of asymmetric magnetization reversal characterized by a sharp step in the second quadrant of the hysteresis loop has been investigated in the exchange biased Co/CoO films. This asymmetry only exists in the film where the small clusters grow to form islands. A bimodal distribution of the first-order reversal curves diagram demonstrates that the irreversible magnetization reversal is composed of the free part and exchange biased part, originating from the grains smaller and larger than 6 nm in the film, respectively. The finite-size effect of the antiferromagnetic anisotropy in the ultrafine grains is responsible for this asymmetry.

Pronounced bipolar resistance switching with a good retention property has been observed in CeO2/PrBa2Cu3O7−δ/Pt heterostructure. The low resistance state and high resistance state exhibited distinguished ferromagnetic signals, as compared to the nearly non-magnetic initial state. It is found that the migration of the oxygen vacancies under electric field is mainly responsible for the electric and the magnetic changes. The modified interfacial electronic structure by the oxygen vacancy migration and the trapping/detrapping of the carriers leads to the resistance switching. The exchange interaction of the hydrogen-like orbitals formed around the singly occupied oxygen vacancies in CeO2 is accounting for the emerged and modulated ferromagnetic signals. Temperature dependence of resistance in the low resistance state follows a variable range hopping law, further confirming that the amount of oxygen vacancies in the CeO2 layer directly affects the hydrogen-like orbital radius, which determines the strength of...

A Monte Carlo method is developed to simulate the magnetoelectric coupling in multiferroic BiFeO3 with coexistence of ferroelastic, ferroelectric, and antiferromagnetic order parameters. Long-range interactions among dipoles and spins are summed through cutoff, while elastic interactions among transformation strain are evaluated using Green’s function method. Short-range interactions among ferroelectric dipoles and antiferromagnetic spins are also considered. Through the Monte Carlo simulation, coupled ferroelastic, ferroelectric, and antiferromagnetic domains are demonstrated, the switching of magnetic spins by electric field is verified, and mechanical switching of spins is also predicted.

Single crystal AlN thin films were epitaxially grown on GaN/sapphire (0001) substrates on a macroscopic scale by magnetron sputtering. The microscopic structure and orientation degree of the AlN epilayers were studied by high-resolution transmission electron microscopy, high-resolution x-ray diffraction, and reciprocal spacing mapping. It was revealed that the AlN epilayers have high in-plane and out-of-plane orientation degrees and low defect density. The electrical and optical properties of the AlN epilayers were also studied, and the results suggest that the AlN epilayers grown by sputtering may be employed in the fabrication of GaN-based light-emitting diode devices with increased efficiency.

The motion of Abrikosov vortices is the dominant origin of dissipation in type II superconductors subjected to a magnetic field, which leads to a finite electrical resistance. It is generally belie...