Search

Infrared metamaterial absorber (MMA) based on metal-insulator-metal (MIM) configuration with flexible design, perfect and selective absorption, has attracted much attention recently for passive radiative cooling applications. To cool objects passively, broadband infrared absorption (i.e. 8–14 μm) is desirable to emit thermal energy through atmosphere window. We present a novel MMA composed of multilayer MIM resonators periodically arranged on a PbTe/MgF2 bilayer substrate. Verified by the rigorous coupled-wave analysis method, the proposed MMA shows a relative bandwidth of about 45% (from 8.3 to 13.1 μm with the absorption intensity over 0.8). The broadband absorption performs stably over a wide incident angle range (below 50°) and predicts 12 K cooling below ambient temperature at nighttime. Compared with the previous passive radiative coolers, our design gets rid of the continuous metal substrate and provides an almost ideal transparency window (close to 100%) for millimeter waves over 1 mm. The structure is expected to have potential applications in thermal control of integrated devices, where millimeter wave signal compatibility is also required.

Coronavirus Disease 2019 (COVID-19), caused by the novel coronavirus, has spread rapidly across China. Consequently, there is an urgent need to sort and develop novel agents for the prevention and treatment of viral infections. A rapid structure-based virtual screening is used for the evaluation of current commercial drugs, with structures of human angiotensin converting enzyme II (ACE2), and viral main protease, spike, envelope, membrane and nucleocapsid proteins. Our results reveal that the reported drugs Arbidol, Chloroquine and Remdesivir may hinder the entry and release of virions through the bindings with ACE2, spike and envelope proteins. Due to the similar binding patterns, NHC (β-d-N4-hydroxycytidine) and Triazavirin are also in prospects for clinical use. Main protease (3CLpro) is likely to be a feasible target of drug design. The screening results to target 3CL-pro reveal that Mitoguazone, Metformin, Biguanide Hydrochloride, Gallic acid, Caffeic acid, Sulfaguanidine and Acetylcysteine seem be possible inhibitors and have potential application in the clinical therapy of COVID-19.

Optical operations have served as the basis of spectroscopy and imaging in terahertz regimes for a long time. Available lenses are practical tools for modulations. We fabricate a kind of biconvex lens from the natural dolomite cluster. The lens works well at 0.1 THz based on the relatively high refractive index and low absorption coefficients. Compared with the lens fabricated by a dolomite stone, such a lens can focus dispersive terahertz beam efficiently in terahertz imaging systems, which indicates that natural minerals hold promising applications in terahertz optics.

Using angle-resolved photoemission spectroscopy, we study the low-energy electronic structure of a layered ternary telluride EuSbTe3 semiconductor. It is found that the photoemission constant energy contours can be well described by the simple two-parameter (t perp and t para ) tight-binding model based on the Te orbitals in square-net planes of EuSbTe 3 , suggesting its Te 5p orbitals dominated low-lying electronic structure, which is reminiscent of other rare-earth tritellurides. However, a possible charge-density-wave gap of 80 meV is found to persist in 300 K, which renders the unexpected semiconducting properties in EuSbTe 3 . Moreover, we reveal an extra band gap occurring around 200 meV below the Fermi level at low temperatures, which can be attributed to the interaction between the main and folded bands due to lattice scatterings. Our findings provide the first comprehensive understanding of the electronic structure of layered ternary tellurides, which lays the basis for future research on these compounds.

Co(II) doped ZnTe nanowires are prepared by a thermal evaporation method. The power and temperature dependent micro-photoluminescence spectra of single nanowire demonstrate the double bands near its band edge, and the ferromagnetism behavior for these nanowires is identified. The occurrence of excitonic magnetic polaron (EMP) can account for the second emission band for its higher binding energy and ferromagnetic coupling. This EMP formation in a nanostructure will facilitate to realize magnetic modulation on confined excitons and will find new applications for spinpolarized nanophotonic devices.

We investigate the anisotropic magnetic transports in topological semimetal TaSb2. The compound shows the large magnetoresistance (MR) without saturation and the metal-insulator-like transition no matter whether the magnetic field is parallel to c-axis or a-axis, except that the MR for B||c is almost twice as large as that of B||a at low temperatures. The adopted Kohler's rule can be obeyed by the MR at distinct temperatures for B||c, but it is slightly violated as B||a. The angle-dependent MR measurements exhibit the two-fold rotational symmetry below 70 K, consistent with the monoclinic crystal structure of TaSb2. The dumbbell-like picture of angle-dependent MR in TaSb2 suggests a strongly anisotropic Fermi surface at low temperatures. However, it finally loses the two-fold symmetry over 70 K, implying a possible topological phase transition at around the temperature where Tm is related to a metal-insulator-like transition under magnetic fields.

The evolution of the recrystallization phase in amorphous 6H-SiC formed by He implantation followed by thermal annealing is investigated. Microstructures of recrystallized layers in 15 keV He ion implanted 6H-SiC (0001) wafers are characterized by means of cross-sectional transmission electron microscopy (XTEM) and high-resolution TEM. Epitaxial recrystallization of buried amorphous layers is observed at an annealing temperature of 900°C. The recrystallization region contains a 3C-SiC structure and a 6H-SiC structure with different crystalline orientations. A high density of lattice defects is observed at the interface of different phases and in the periphery of He bubbles. With increasing annealing to 1000°C, 3C-SiC and columnar epitaxial growth 6H-SiC become unstable, instead of [0001] orientated 6H-SiC. In addition, the density of lattice defects increases slightly with increasing annealing. The possible mechanisms for explanation are also discussed.

The properties of the low-lying states and the shape coexistence in 98Sr are investigated within the framework of the proton—neutron interacting boson model (IBM2). By considering the relative energy of the d proton boson to be different from that of the neutron boson, it is found that the calculated energy levels and the B(E2) transition strengths agree with the experimental data perfectly. Particularly, the second 0+ state, which is associated with the shape coexistence phenomenon and has the lowest energy E(02 +) among all known even—even nuclei, is reproduced very well. The behavior of the calculated quadrupole shape invariants is consistent with the experimental results.

The objective of this study is to find an effective method to improve Voc without Jsc loss for Cu2ZnSnSe4 (CZTSe) thin film solar cells, which have been fabricated by the one step co-evaporation technique. Surface sulfurization of CZTSe thin films is carried out by using one technique that does not utilize toxic H2S gas; a sequential evaporation of SnS after CZTSe deposition and the annealing of CZTSe thin films in selenium vapor. A Cu2ZnSn(S,Se)4 (CZTSSe) thin layer is grown on the surface of the CZTSe thin film after the annealing. The conversion efficiency of the completed device is improved due to the enhancement of Voc, which could be attributed to the formation of a hole-recombination barrier at the surface or the passivation of the surface and grain boundary by S incorporation.

The performance of a passively Q-switched all-solid-state Nd:YVO4 laser using Cr4+:YAG as saturable absorber is reported. Optimum coupling operation at 1064 nm resulted in 70 ns pulses at 40 kHz repetition rates with average output power of 2.1 W. A quantitative theoretical description agrees well with the experimental results.

With a type-I noncritically phase-matched LiB3O5 crystal as the intracavity frequency doubler in a diode pumped Nd:YVO4 laser, 440 mW of 671 nm light was obtained at 5.5 W of incident pump power, the optical-optical conversion efficiency being 8.0%.

A new interlayer is successfully used to be a universal carrier switch, developing high-performance hybrid white organic light-emitting diodes (WOLEDs). By dint of this interlayer, the two-color hybrid WOLED shows a maximum total current efficiency (CE) and power efficiency (PE) of 48.1 cd/A and 37.6 lm/W, respectively, while the three-color hybrid WOLED shows a maximum total CE and PE of 33.8 cd/A and 25.7 lm/W, respectively. The color rendering index of the three-color hybrid WOLEDs are ≥75, which is already a sufficient level for many commercial lighting applications. In addition, both the two-color and three-color hybrid WOLEDs show low efficiency roll-off and stable color. Furthermore, devices with the new interlayer show much higher performance than devices with the most commonly used 4,4-N,N-dicarbazolebiphenyl and N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine interlayers.

The cross sections of fragments produced in the 140 A MeV58,64Ni+9 Be projectile fragmentation reactions are calculated by using the antisymmetrized molecular dynamics (AMD) model, the modified statistical abrasion-ablation (SAA) model, and the empirical EPAX2/EPAX3 formulae. The Gogny-g0 interaction is taken as the effective nucleon-nucleon interaction in the AMD calculation, and the decays of fragments obtained from the AMD results are calculated by using the GEMINI code. The calculated cross sections of fragments are compared.

We investigate the properties of the low-lying states and the relevant shape dynamics of 98Mo within the framework of the proton-neutron interacting boson model (IBM2). By considering the relative energy of the d proton boson to be different from that of the neutron bosons, the low-lying levels and the key observable B(E2) transition branching ratios are calculated. The characteristic feature of the energy spectrum and the most crucial available structure indicator indicate that the substantial mixing between the spherical-vibrational and γ-unstable shapes in 98Mo. The calculation results of the overall deformation in 98Mo are almost the same for both the ground and the first excited 0+ states, showing a weak deformation. While the triaxiality parameter indicates that the mostly triaxial shape with some oblate for the ground state, and the triaxial shape with some prolate for the excited 0+2 state, being equilibrium shapes of spherical-vibrational and γ-unstable in 98Mo.

Using the Cerenkov second harmonic generation, 478nm blue and 402nm violet light are generated by direct frequency doubling of 956 and 804nm diode lasers in a same proton exchanged MgO:LiNbO3 waveguide. Under the low fundamental guide wave power of less than 1 mW, the estimated value of the output blue and violet light power is in the order of 0.1-0.01μW.

The influence of strain accumulation on optical properties is investigated for InGaN/GaN-based blue light-emitting diodes grown by metal organic vapor-phase epitaxy. It is found that it is possible to reduce the strain relaxation and hence the nonradiative recombination centers in InGaN multi-quantum wells (MQWs) by adopting more InGaN/GaN MQWs pairs. The alleviation of strain relaxation in a superlattice layer results in the crystalline perfection and effective quality improvement of the epitaxial structures. With suitable control of the crystalline quality and reduced strain relaxation in the MQWs, there shows a 4-fold increase in light output luminous efficiency as compared to their conventional counterparts.

We describe the properties of low-lying states of 102Ru within the framework of the proton-neutron interacting model IBM2. The theoretical predictions of the ground state, quasi-γ and quasi-β bands, and the ratios of the B(E2) transition strengths are reproduced very well. The structural properties of 102Ru are identified in the parameters space of the interacting boson model (IBM2). The characteristic feature of the energy spectrum structure exhibits that 102Ru is very close to the critical point of Uπv(5)—Oπv(6) transition and towards Uπv(5) symmetry. The key sensitive quantities of the B(E2) branching ratio clearly indicate that 102Ru is a primary Oπv (6) symmetry, while with a somewhat Uπv (5) symmetry. It is possible that the shape coexistence persists in 102Ru, whereas the evident fingerprint of the shape coexistence has not been observed.

We present the fabrication of flexible Cu(In,Ga)Se2 (CIGS) solar cells on a polyimide (PI) sheet with and without Na incorporation. A sodium element is incorporated into the CIGS absorber by using a NaF precursor after Mo back contact deposition. X-ray diffraction patterns show that the (112) preferred orientation of the as-grown CIGS films is decreased by Na incorporation. The secondary phase of (Inx,Ga1−x)2Se3 is observed for the CIGS films with Na. There is no significant difference in the grain size with and without Na incorporation from surface and cross-sectional SEM images. Additionally, the increase of carrier concentration and decrease of resistivity of CIGS absorber are induced by Na doping. Finally, the flexible CIGS solar cells on PI sheets with efficiency close to 11%, containing Na, are achieved. The improvement of cell efficiency can be attributed to the modified electrical properties of the CIGS film by Na incorporation.

A superfluorescent fiber source (SFS) based on an Er3+-doped photonic crystal fiber (EDPCF) is reported. Owing to the temperature insensitivity of the EDPCF, we show that it is possible to improve the mean wavelength stability of an SFS. Using single-backward configuration, the EDPCF SFS mean wavelength variation at temperatures from −40°C to 60°C is less than 100 ppm, indicating that the thermal coefficient of the EDPCF is smaller than 1 ppm/°C and 3–6 times smaller than those of two conventional Er3+-doped fibers under the same experimental conditions. The best performance of the EDPCF-based SFS is obtained between 0°C and 60°C, at which the change in the mean wavelength is only 17.445 ppm.

Idea spreading is an important process in science and society. In this work, we study this spreading process in a population consisting of two groups based on a recent model proposed by Bornholdt et al. We consider two types of division in the population: regular and random division. We find some interesting phenomena, for example, the exchange of dominant ideas between the two groups in the cases of regular and the random division, and the appearance of a novel stage in which a few ideas interact strongly to seek a balance.

The time-dependent non-thermal particle and photon spectra are reproduced for a Type Ia SNR Tycho with radio, x-ray, GeV and TeV emission within the framework of the diffusive shock acceleration of the non-thermal particles. TeV photons can come from the inverse Compton scattering of relativistic electrons and from the π0-decay process in proton-proton interaction. The results show that (1) the hadronic case can model the observed multiwavelength spectrum well and, peculiarly, the π0-decay process appears to be necessary to explain the GeV emission; and (2) magnetic field amplification is vital in the SNR.

Coupled Korteweg-de Vries (KdV) systems have many important physical applications. By considering a 4 × 4 spectral problem, we derive a discrete coupled KdV-type equation hierarchy. Our hierarchy includes the coupled Volterra system proposed by Lou et al. (e-print arXiv:0711.0420) as the first member which is a discrete version of the coupled KdV equation. We also investigate the integrability in the Liouville sense and the multi-Hamiltonian structures for the obtained hierarchy.

The chiral doublet bands in 135Nd and 136Nd are investigated systematically within the supersymmetry scheme including many-body interactions and possessing the SO(5)(or SU(5)) symmetry on the rotational symmetry. Quantitatively good results of the energy spectra, the energy staggering parameter as a function of the spin and the spin assignment are obtained. The calculation shows that the stronger competition between the pairing and anti-pairing effects exists in these chiral doublet bands and the SU(3) symmetry breaking more seriously exists in the stable chiral structure.

Approximate generalized conditional symmetry is developed to study the approximate symmetry reduction for initial-value problems of the extended KdV-Burgers equations with perturbation. These equations can be reduced to initial-value problems for some systems of first-order perturbed ordinary differential equations in terms of a new approach. Complete classification theorems are obtained and an example is taken to show the main reduction procedure.