Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Based upon the new designed helical resonator, the RF resonant frequency for trapping ions can be consecutively adjusted in a large range (about 12 MHz to 29 MHz) with high Q-factors (above 300). We analyze the helical resonator with a lumped element circuit model and find that the theoretical results fit well with experiment data. With our resonator system, the resonant frequency near magic RF frequency (where the scalar Stark shift and the second-order Doppler shift due to excess micromotion cancel each other) can be continuously changed at kHz level. For <jats:sup>88</jats:sup>Sr<jats:sup>+</jats:sup> ion, compared to earlier results, the measurement accuracy of magic RF frequency can be improved by an order of magnitude upon rough calculation, and therefore the net micromotion frequency shifts can be further reduced. Also, the differential static scalar polarizability △<jats:italic>α</jats:italic> <jats:sub>0</jats:sub> of clock transition can be experimentally measured more accurately.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The intercalation of heteroatoms between graphene and metal substrates is a promising method for integrating epitaxial graphene with functional materials. Various elements and their oxides have been successfully intercalated into graphene/metal interfaces to form graphene-based heterostructures, showing potential applications in electronic devices. Here we theoretically investigated the hafnium intercalation between graphene and Ir(111). We find that the penetration barrier of Hf atom is significantly large due to its large atomic radius, which suggests that hafnium intercalation should be carried out with low deposition doses of Hf atoms and high annealing temperatures. Our results show the different intercalation behaviors of a large-size atom and provide guidance for the integration of graphene and hafnium oxide in device applications.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper puts forward a novel method for measuring the thin period-structure-film thicknesses based on the Bloch surface wave (BSW) enhanced Goos-Hänchen (GH) shift in one-dimensional photonic crystal (1DPC). The BSW phenomenon presented in 1DPC enhances the GH shift generated in the attenuated total internal reflection structure. The GH shift is closely related to the thickness of the film which composed by layer-structure of 1DPC. GH shifts in multiple different incident light conditions will be obtained by varying the wavelength and angle of the measured light, and the thickness distributions of the entire structure of 1DPC will be calculated by the Particle Swarm Optimization (PSO) algorithm. The relationship, between the structure of a 1DPC film composed of TiO<jats:sub>2</jats:sub> and SiO<jats:sub>2</jats:sub> layers and the GH shift, is specially investigated. Under the specific photonic crystal structure and incident conditions, a giant GH shift, 5.1 × 10<jats:sup>3</jats:sup> times of the wavelength of incidence, can be obtained theoretically. Simulation and calculation results show that it is capable to measure the thicknesses of termination layer and periodic structure layers of 1DPC films with 0.1 nm resolution by measuring the GH shifts. The exact structure of a 1DPC film is innovatively measured by the BSW enhanced GH shift.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The rapid development of two-dimensional (2D) materials offers new opportunities for 2D ultra-thin excitonic solar cells (XSCs). The construction of van der Waals heterostructures (vdWHs) is a recognised and effective method for integrating the properties of single-layer 2D materials, and creating particularly superior performance. Here, the prospects of h-BP/h-BAs vdW heterostructures in 2D excitonic solar cells are assessed. We have systematically investigated the electronic properties and optical properties of heterogeneous structures, based on density functional theory (DFT) and using first-principles methods calculations. The results indicated that the heterogeneous structure has good optoelectronic properties, such as a suitable direct bandgap and excellent optical absorption properties. The calculation of the phonon spectrum also confirms the well-defined kinetic stability of the heterstructure. We have designed heterogeneous structures as a model for solar cells, and calculated its solar cell power conversion efficiency up to 16.51%, which is higher than the highest efficiencies reported in organic solar cells (11.7%). Our work illustrates the potential of h-BP/h-BAs heterostructure as candidates for 2D excitonic solar cells with high efficiency.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Two substrate integrated waveguide (SIW) cavity antenna arrays based on metasurface are proposed in this paper. By rotating the metasurface element, circularly polarized and high gain antennas are achieved respectively. Firstly, multi-mode resonance theory is employed to broaden the bandwidth of the slot antenna. And then, a SIW cavity composed of 4×4 corner cut elements is added on the top of the slot antenna to achieve the circular polarization and improve the front-to-back ratio. Thirdly, the metasurface elements are sequentially rotated and a high gain antenna with 2 dBi enhancement average in the operation band is obtained. Based on the two antenna units, two 2×2 antenna arrays are designed. Both of the circularly polarized and high gain antenna arrays are fabricated to verify the correctness. What’s more, the novel wideband phase shifter is employed in the circularly polarized antenna to obtain the operating bandwidth of 38% (4.05-5.95 GHz) and AR bandwidth of 24.9% (4.4-5.65 GHz). The bandwidth of the high gain antenna can reach 42.7% (3.95-6.1 GHz) and with the gain enhancement of 2 dBi compared to the circularly polarized antenna. The gain remains steady in most operating band within a variation of 1 dBi. It is remarkable that the rotating of the metasurface element has a great influence on the antenna performance which provides a new explication for the multi-function antenna design.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Since a hole barrier was formed in back contact due to mismatch of work function, back contact material for CdTe cell has always been a significant research direction. ZnTe:Cu was ideal back contact material, which reduced the valence band discontinuity and can be used as the electron back reflection layer to inhibit interface recombination. The conductivity of ZnTe:Cu film was improved by applying RF coupled DC sputtering and post-deposition heat treatment. The doping efficiency was computed as the ratio of free hole density and copper concentration, which could be correlated with performance for CdTe-based solar cell. The higher doping efficiency meant that more copper substitute Zn sites in ZnTe lattices and less mobilized copper remained which could enter the CdTe absorber layer. Copper was suspected as dominant element for of CdTe-based cell degradation. After optimizing ZnTe:Cu films, a systematic study was carried out to incorporate ZnTe:Cu film to CdTe solar cell. EQE spectral kept relatively stable over the long wavelength range without decreasing. It was proved that the conduction band barrier of device with ZnTe:Cu/Au contact materials had an effect on the EQE response, which worked as free electron barrier and decreased the recombination rate of free carrier. According to dark <jats:italic>J-V</jats:italic> data or the linear region of light <jats:italic>J-V</jats:italic> data, current indicated that the intercept gave diode reverse saturation current. The results of ideality factor indicated that the dominant recombination occurred in the space charge region. In addition, the space charge density and depletion width of solar cell can be estimated by <jats:italic>C-V</jats:italic> profiling.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Turbulence characteristics of plasmas with the internal transport barriers in HL‐2A tokamak are analyzed by means of linear gyrokinetic simulations. It is found that turbulence is dominated by the Ion Temperature Gradient (ITG) mode together with large scale modes characterized by high‐frequency electromagnetic fluctuation, which are destabilized by the steep ion temperature gradient in weak magnetic shear regime. Comparison with solutions of analytical dispersion relations shows that their linear features match well with the beta‐induced Alfven eigenmode (BAE) branch of shear Alfvenic spectrum. It is further clarified that the large population of fast ions in these plasmas play a stabilization role through the dilution mechanism in high‐n ITG mode regimes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Comprehension of the heat transport within living biological tissues is crucial to effective heat treatments. The heat transport properties of living biological tissues with temperature-dependent properties are explored in this paper. Taking into account of variable physical properties, the governing equation of temperature is first derived in the context of the dual-phase-lags model (DPL). An effective method, according to the Laplace transform and a linearization technique, is then employed to solve this non-linear governing equation. The temperature distribution of a biological tissue exposed to a pulse heat flux on its exterior boundary, which frequently happens in various heat treatments, is predicted and analyzed. The results state that a lower temperature has been predicted when the temperature dependence is considered in the heating process. The contributions of key thermal parameters are different and dependent on the ratio of phase lags and the amplitude of the exterior pulse heat flux.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A systematic study is made on the time-dependent dynamic transport characteristics of the side-coupled double quantum-impurity system based on the hierarchical equations of motion. It is found that the transport current behaves like a single quantum dot when the coupling strength is low during tunneling or Coulomb coupling. For the case of only tunneling transition, the dynamic current oscillates due to the temporal coherence of the electron tunneling device. The oscillation frequency of the transport current is related to the step voltage applied by the lead, while the <jats:italic>T</jats:italic>, e-e interaction <jats:italic>U</jats:italic> and the bandwidth <jats:italic>W</jats:italic> have little influence. The amplitude of the current oscillation exists in positive correlation with <jats:italic>W</jats:italic> and negative correlation with <jats:italic>U</jats:italic>. With the increase in coupling <jats:italic>t</jats:italic> <jats:sub>12</jats:sub> between impurities, the ground state of the system changes from a Kondo singlet of one impurity to a spin-singlet of two impurities. Moreover, lowering the temperature could promote the Kondo effect to intensify the oscillation of the dynamic current. When only the Coulomb transition is coupled, it is found that the two split-off Hubbard peaks move upward and have different interference effects on the Kondo peak at the Fermi surface with the increase in <jats:italic>U</jats:italic> <jats:sub>12</jats:sub>, from the dynamics point of view.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We theoretically investigate high-order harmonic generation (HHG) in crystals induced by linearly polarized laser fields. We obtain the HHG spectra by solving the semiconductor Bloch equations and analyze the radiation process by different models. Here we propose a multiple collision model, in which the electrons and holes are produced at different times and places. It is found that the multiple collision trajectories can help us comprehensively and better explain the results of the quantum calculation. Moreover, we find that the harmonic suppression occurs due to the overlap of multiple collision trajectories.</jats:p>