Tunable metamaterial absorber based on resonant strontium titanate artificial atoms

Dynamic control of the absorption frequency and intensity of metamaterial absorbers has attracted considerable attention,and many kinds of tunable metamaterial absorbers have been proposed.Unfortunately,due to the integration of separate resonant unit and tunable unit,these designed metamaterial absorbers suffer from complex structure and low sensitivity.We numerically and experimentally demonstrate a tunable metamaterial absorber composed of artificial dielectric atoms as both resonant and tunable unit arrayed periodically in the background matrix on the metallic plate.Polarization insensitive and wide incident angle absorption band with simulated and experimental absorptivity of 99%and 96%at 9.65 GHz are achieved at room temperature.The absorption frequency can be gradually modulated by temperature,however,the absorption intensity at working frequency remains near unity.The dielectric atoms based tunable metamaterial absorbers with simple structure have potential applications as tempe rature sensors and frequency selective thermal emitters.

Oxygen vacancy promoting artificial atom(RuPd)by d-orbital coupling for efficient water dissociation

Rational design of highly active catalysts for breaking hydrogen-oxygen bonds is of great significance in energy chemical reactions involving water.Herein,an efficient strategy for the artificial atom(RuPd)established by d-orbital coupling and adjusted by oxygen vacancy(V_(O))is verified for water dissociation.As an experimental verification,the turnover frequency of RuPd-TiO_(2)-VO(RuPdTVO)catalyst in ammonia borane hydrolysis reaches up to 2750 min^(−1)(26,190 min−1 based on metal dispersion)in the absence of alkali,exceeding the highest active catalysts(Rh-based catalysts).The d-orbital coupling effect between Ru and Pd simulates the outer electronic structure of Rh.Electron transfer from V_(O) to(RuPd)constructs an electron-rich state of active sites that further enhances the ability of the artificial atom to dissociate water.This work provides an effective electronic regulation strategy from V_(O) and artificial atom constructed by d-orbital coupling effect for efficient water dissociation.

Kondo Effect in a Quantum Dot Coupled to Ferromagnetic Leads and a Mesoscopic Ring

Using an equation of motion technique, we investigate the Kondo effect in a quantum dot coupled to ferromagnetic leads and a mesoscopic ring. It is shown that the Kondo resonance at the Fermi level of the dot presents the periodic change along with the aggrandizement of the magnetic flux and the number of lattice sites NR in the mesoscopic ring, and for the antiparallel spin alignment the Kondo resonances for spin-up and spin-down configurations appear at the same position. However, for the parallel spin alignment, the Kondo resonance splits for the spin-up and spin-down configurations.

Energy levels and states of parabolic cylindrical lens shaped quantum dots

The parabolic cylindrical lens shaped quantum dot is investigated theoretically. The Schrǒdinger equation for an electron confined in this structure is solved in the parabolic cylindrical coordinate system. The wavefunctions for the electron are presented in terms of confluent hypergeometric functions, and the electron energy spectra are also obtained.

Ground State of a Two-Electron Quantum Dot with a Gaussian Confining Potential

We investigate the ground-state properties of a two-dimensional two-electron quantum dot with a Gaussian confining potential under the influence of perpendicular homogeneous magnetic field. Calculations are carried out by using the method of numerical diagonalization of Hamiltonian matrix within the effective-mass approximation. A ground-state behaviour （singlet→triplet state transitions） as a function of the strength of a magnetic field has been found. It is found that the dot radius R of the Gaussian potential is important for the ground-state transition and the feature of ground-state for the Gaussian potential quantum dot （QD）, and the parabolic potential QDs are similar when R is larger. The larger the quantum dot radius, the smaller the magnetic field for the singlet-triplet transition of the ground-state of two interacting electrons in the Gaussian quantum dot.

Singlet-Triplet Transition in Quantum Dots Confined by Triangular and Bowl-Like Potentials： the Effect of Electric Fields

We theoretically investigate the energy spectra of two-electron two-dimensional （2e 2D） quantum dots （QDs） confined by triangular potentials and bowl-like potentials in a magnetic field by exact diagonalization in the framework of effective mass theory. An in-plane electric field is found to contribute to the singlet-triplet transition of the ground state of the 2e 2D QDs confined by triangular or bowl-like potentials in a perpendicular magnetic field. The stronger the in-plane electric field, the smaller the magnetic field for the total spin of the ground states in the dot systems to change from S = 0 to S = 1. However, the influence of an in-plane electric field on the singlettriplet transition of the ground state of two electrons in a triangular QD modulated by a perpendicular magnetic field is quite small because the triangular potential just deviates from the harmonic potential well slightly. We find that the strength of the perpendicular magnetic field needed for the spin singlet-triplet transition of the ground state of the QD confined by a bowl-like potential is reduced drastically by applying an in-plane electric field.

Relationship between atomic structure and crystal type studied by artificial neural network

We have used chemical bond parameters and pattern recognition method to investigatethe regularities of the crystal type of alloy phase,and achieved good results.Theparameters used,however,are semi-empirical paramters,which are not very strict fromtheoretical viewpoint.In this letter,we use the numbers describing atomic structure(thenumbers of valence electrons Z1,Z2,the principal quantum numbers of valence electrons n1,