For a lattice Boussinesq equation, we introduce a simple-parameter invertible transformation by which the equation is transformed into an extended version. This new equation admits solitons and nonzero quasi-rational solutions, both in Casoratian form. These solutions can be reverted to those of the lattice Boussinesq equation.

We propose a protocol for transferring photons of unknown states to a distant location using path-polarization hybrid entanglement. Our protocol uses a polarizing beam splitter (PBS), a beam splitter (BS), a CNOT-operation, four unitary operations and polarizing detectors. In our protocol, the hybrid entangled states are generated by the PBS, and it is transmitted through the quantum channel containing the BS and CNOT-gate. The measurement results of the polarizing detectors and classical communications determine which unitary operation will be used in the last step for recovering initial states. The security of the channel in transmitting unknown photons between two parties is confirmed by the results of the measurement of each target photon in the control mode.

Based on Yang's quantized space-time model, a complete Yang model from (5+1)-dimensional space with Minkowski signature is discussed using the projective geometry method and Dirac procedure. We introduce an anti-Yang model and an anti-Snyder model to discuss the duality relations between the anti-Snyder model and anti-de Sitter special relativity.

A family of exact analytical solutions of vortices in quantum fluid governed by a two-dimensional time-dependent Schr?dinger equation is presented, which describes different kinds of vortex structures. The dynamics of different vortex clusters, such as the single vortex, vortex pair, vortex dipole and vortex trimer in a two-dimensional quantum fluid are analytically studied based on these exact solutions. The time evolutions of the wave of such vortices are demonstrated, and the orbits of motion of singular points in the vortices are also explored. The interactions of vortices in many-vortex clusters are discussed. A repulsive interaction between vortices with the same topological charge, and inter-annihilation and inter-creation of vortices with opposite topological charge, are shown.

We investigate bright, dark and two rogue waves in two-component Bose–Einstein condensates. It is found that one rogue wave of a new structure that contains two humps and two valleys around one center in the temporal-spatial distribution interacts with the conventional rogue wave. We present an effective way to obtain long-lived rogue waves through managing the nonlinear interaction with modulating trapping frequency and interchange atoms between thermal clouds and condensates. The results provide many possibilities to manipulate rogue waves experimentally in the condensate system.

The security of controlled bidirectional quantum direct communication using a GHZ state [Chin. Phys. Lett. 23 (2006) 1680] is analyzed. It turns out that the MX protocol has the problem of definite information leakage, i.e., the first bit of a secret message from any communication party is always leaked out without any active attack after the controller's announcement of measurement results. We put forward two approaches to improve this. The first is to merely modify the encoding rule of the MX protocol, while the second is to use a Bell state as the quantum resource instead of a GHZ state. Both our approaches can ensure that all the bits of secret messages from two communication parties are not leaked out after the controller's announcement of measurement results. Moreover, the controlled bidirectional quantum secure direct communication protocol based on the second approach is more convenient to implement than the MX protocol, since it merely uses a Bell state as the quantum resource and only needs to perform the Bell-basis measurement.

We study magneto-transport through a weakly open circular microstructure in the perpendicular weak magnetic fields by a semiclassical approximation within the framework of the Fraunhofer diffraction effect at the lead openings. It is found that the peak positions of the transmission power spectrum can be related to simple trajectories according to classical dynamics. Moreover, we formulate the fluctuations in the transmission amplitude as functions of both the wave number k and the magnetic field B in terms of different classical trajectories, and the Aharonov–Bohm phase of the directed areas enclosed by these trajectories that reflect the quantum interference effect.

We study constructive generalized synchronization (GS) for bidirectional discrete arrays of difference systems (BDADSs). The result provides a general representation of GS in BDADSs. Numerical simulations are presented to show the effectiveness of the theoretical results.

We present an active optical clock scheme with a four-level quantum potassium system. We calculate the population probabilities of each state using the density matrix. At the steady state, ρ₃₃ and ρ₅₅ are equal to 8.3% and 3.5%, respectively, and the population inversion between the 5S_1/2 and 4P_3/2 states is built up in the thermal potassium cell with a 404.7 nm pumping laser. According to the mechanism of the active optical clock, under the action of the 404.7 nm pumping laser, the scheme can output a 1252.2 nm quantum-limited-linewidth laser, which can be directly used as an active optical frequency standard.

A novel Mach–Zehnder (M-Z) interferometer used to measure the dispersion and phase shift of a light beam is reported. The interferometer consists of two identical beam displacing polarizers, which makes two beams of interference light pass through the same optical device and greatly improves the stability of the M-Z interferometer. The basic method of dispersion and phase measuring through the present interferometer is introduced in detail, and the actual application is demonstrated by a specific example. Because the measuring of dispersion and phase shift is the heating point in the field of optics, it is obvious that the M-Z interferometer will have important applications in aspects of optics, especially quantum optics and optical information processing.

The index sensing characteristics of metallic deep gratings are numerically investigated. The concept is based on magnetic polariton resonance, which is very sensitive to changes in the refractive index of the surrounding medium. We numerically demonstrate that the sensitivity and figure of merit of the magnetic plasmon mode can be tailored by adjusting the depth and width of the slits. The highest sensitivity of 1542 nm per refractive index unit with a good figure of merit of 12.3 is obtained. The angle-insensitive property with a high signal intensity of this system could be useful for the future design and application of wide-range sensitive plasmonic index sensors.

A through-wall image enhancement scheme is proposed based on principal component analysis and minimum description length criterion. The minimum description length criterion is used with principal component analysis to extract target eigen components. The proposed scheme is capable of extracting multiple targets from heavy cluttered through-wall images. The results of the proposed scheme are compared with existing schemes on the basis of quantitative analysis and visual inspection.

It is believed that one can extract more accurate information of the pion distribution amplitude from the pion-photon transition form factor (TFF) due to the single pion in this process. However, the BABAR and Belle data of the pion-photon TFF have a big difference for Q²∈[15,40] GeV², and at present, the pion DA can not be definitely determined from the pion-photon TFF. It is crucial to find the right pion DA behavior and to determine which data is more reliable. We perform a combined analysis of the most existing data of the processes involving pion by using a general model for the pion wavefunction/DA. Such a DA model can mimic all the existed pion DA behaviors, whose parameters can be fixed by the constraints from the processes π⁰→γγ, π→μν, and B→πl ν, etc. Especially, we examine the B →π transition form factors that provides another constraint to the parameter B in our DA model, which results in B∈[0.00,0.29]. This inversely shows that the predicted curve for the pion-photon TFF is between the BABAR and Belle data in the region Q²∈[15,40] GeV². It will be tested by coming more accurate data in large Q² region, and the definite behavior of pion DA can be concluded finally.

We report on the first observation of the neutron-rich nucleus ¹³¹Ag. This isotope was produced via fragmentation reactions of intense secondary radioactive ion beams, including ^{134, 135}Sn. The secondary beams were produced from induced fission reactions from a stable ²³⁸U beam at 345 MeV/nucleon. Secondary reaction residues were selected by the ZeroDegree spectrometer and identified by measuring their magnetic rigidity, time of flight, energy loss, and total kinetic energy.

We introduce a new surface energy coefficient in proximity formalism, which is dependent on temperature, and apply it to a systematic study of barrier height and position. This proximity model can effectively predict the barrier heights and positions, as well as the fusion cross sections, over a wide range of incident energies, especially in light-heavy nuclei interaction.

An accurate method combining the spheroidal coordinate and B-spline for H₂⁺ is tested. The equilibrium distances and the total energies of the states with |m|≤4 for the magnetic field strength γ=1 are given and compared with those obtained using different methods. Taking the advantages of the spheroidal coordinate and B-spline, a 10^?9–10^?12 accuracy is obtained for the energies of the states with |m|≤3, and a 10^?5–10^?7 accuracy for the equilibrium distances. There are seven significant digits for the energy of the state 1γ_g and four significant digits for 1γ_u, which are consistent with those obtained by the high-precision method. There are three significant digits for the equilibrium distances of the 1γ_g,u states, which are consistent.

Titanium dioxide (TiO₂) nanotubes have been widely investigated for their potential applications in solar cells, hydrogen production, and catalysis. We study three types of TiO₂ nanotubes constructed from anatase TiO₂ monolayers with density functional-based tight binding methods employing the DFTB+ code. The dependences of the strain energies, structural and electronic properties on the radii of the tubes are investigated in the 3–10 ? range. In addition, the present calculations indicate that the electronic band gap of all types of TiO₂ nanotubes is proportional to their diameters. Chiral (n,m) tubes have smaller band gaps than (n,0) and (m,0) tubes, which can be prepared for absorbing the visible spectrum of solar energy.

The influence of an ionizing laser on the pump-probe spectra of ⁸⁷Rb over the transition 5²S_1/2,F=2 →5²P_3/2,F'=3 is experimentally studied in an operating magneto-optical trap. These spectral features, including gain peak, a dispersion-like structure and absorption peak, become weak as the intensity of the ionizing laser increases. Moreover, the profiles of the absorption peak and gain peak vary as the ionizing laser intensity changes. Such results indicate that there is more than one component in the two features and that each component has different dependences on the number of ⁸⁷Rb atoms.

We propose a novel method for image encryption, which is realized by the Collins formula with the random shifting method. The Collins formula can denote different optical transforms by one expression with different ABCD elements. For a generalized optical system, the ABCD elements can be randomly chosen, so the keys are increased and the security of the system is strengthened. Finally, some computer simulations are given for different encryption systems to prove the possibilities. The encryption effect is good, and people without the correct keys can not obtain the information easily.

We design a set of processing devices to drill the shaped holes of turbine blades by using a femtosecond laser which outputs 1064 nm 5 W pulses at 100 kHz, investigate the mechanism of the femtosecond laser interaction with metals, and demonstrate that ultrafast laser drilling has distinct strong points against electric spark and longer laser pulse processing. The advantages related to no recast layer, no thermal effect, no micro crack, high precision, and high processing efficiency are carried out.

We investigate the continuous variable entanglement in a four-level atom according to the criterion proposed by Duan et al. [Phys. Rev. Lett. 84 (2000) 2722]. The atomic coherence is introduced using two external classical driving fields. We study the steady-state entanglement of the system in the presence of losses, concluding that the creation of entangled states can be achievable under certain conditions.

Spike train of uneven duration or delay (STUD) pulses hold potential for laser-plasma interaction (LPI) control in laser fusion. The technique based on time grating is applied to generate an STUD pulse train. Time grating, a temporal analogy of the diffraction grating, can control the pulse width, shape, and repetition rate easily through the use of electro-optical devices. The pulse width and repetition rate are given by the modulation frequency and depth of the phase modulation function in theory and numerical calculation. The zero-chirped phase modulation is good for the compression effect of the time grating. A principle experiment of two pulses interfering is shown to verify the time grating function.

An exponential-doping structure is successfully applied to the preparation of AlGaAs/GaAs photocathodes through the metalorganic chemical vapor deposition (MOCVD) technique. The experimental results show that the quantum efficiency in the entire waveband region for the exponential-doping photocathodes grown by MOCVD is remarkably enhanced as compared to those grown by molecular beam epitaxy. As a result of the improved built-in electric fields and cathode performance parameters, the photoemission characteristics for the MOCVD-grown transmission-mode and reflection-mode AlGaAs/GaAs photocathodes are different over the wavelength region of interest.

It is predicted theoretically that a one-dimensional photonic crystal (PC) with a defect layer has an incident-angle dependent transmittance. Growing a multilayer of this PC structure on a BK7 glass substrate by means of thermal vacuum evaporation, we have experimentally measured its transmittance at near-infrared wavelength. The measured transmittance are in good agreement with the theoretical prediction if the influence of random errors in the layer thicknesses resulting from the deposition process is excluded. This work suggests that a one-dimensional PC with a defect layer can be fabricated as a two-dimensional near-field low-pass spatial filter.

Silicate glasses co-doped with Al metal powder and Bi₂O₃ are prepared. The effects of Al on spectral properties of samples are studied. It is found that the absorption intensity increases with increasing Al concentration in bismuth doped silicate glasses. The near-infrared (NIR) emission of the samples can be controlled by Al powder concentration no matter whether or not excited by 808 nm or 976 nm lasers. Furthermore, the influence of Al on formation of Bi-NIR active ions is discussed. The dependence relationship between the emission property of ～416 nm and Al concentration is a way to investigate the NIR emission origin of bismuth doped glass.

A scheme of double grating expanders is first proposed for high energy chirped pulse amplifiers. It is demonstrated that they can compensate for the amplifier's material dispersion up to the fourth-order, together with a suitable grating compressor. The scheme makes it possible that the pulse expansion in Chirped pulse amplifiers (CPAs) is no longer restricted by the material dispersion, and the corresponding grating compressor can be independently optimized according to the available gratings' size and damage threshold.

We present a 397-nm frequency-doubling system with a quasi-phase-matched KTP crystal (PPKTP) which features tunable, narrow linewidth, high power, and excellent mechanical stability. Using 20-mm and 30-mm-long PPKTP crystals, we establish two experimental setups based on different external cavity parameters. By testing the beat signal of these two lasers, the linewidth for the system is measured to be less than 2.5 MHz. The maximum power of blue light can be achieved up to 40 mW. With these performance characteristics, the constructed blue laser system is useful for applications in cold atom physics and precision measurements.

With a microscopic imaging system composed of microscopic objective, lens and CCD, we observe the complicated structures in the speckle fields on the surface of a rough screen. It is found that such structures contain ridge stripes, large platform-like grains, and shivy grains, exhibiting multiple scales in size and multiple fractalities. Simulations shows these structures are formed by different parts of the rough surface. The experimental curve of the autocorrelation function of the speckle intensity includes the three parts of the central peak, the transition part and the long tail part. Using the sum of self-affine fractal models with different scales and fractalities, we propose theoretically a triple-scale autocorrelation function to describe the speckle field. Fit of this autocorrelation function to the experimental curve gives the values of such parameters as average speckle sizes and fractalities in different scales of the speckle structures.

The band structure and transmission coefficient of the two-dimensional ternary locally resonant phononic crystal are computed by the finite element method with the calculated frequency up to 120 kHz. The band gap in the high frequency range is found and considered as the Bragg band gap in the locally resonant phononic crystal which has the locally resonant band gap in the low frequency range normally. Then, a composite phononic crystal by hybridizing the Bragg scattering phononic crystal and the locally resonant phononic crystal is proposed. Simultaneous Bragg and locally resonant band gaps are displayed and discussed for the composite phononic crystal. The results show that the simultaneous Bragg band gap and locally resonant band gap can be tuned.

Patterns such as periodic subharmonic waves and kink-pairs are observed experimentally in a two-dimensional vertically vibrated granular layer located in an annular channel which has a sawtooth-shaped base. Using the thickness of the granular layer and external excitation as control parameters, we find the transitions between different patterns in the layer. The dependence of the kink-pair's velocity on the external excitation is revealed. The local velocity fields of the granular layer indicate that, in addition to horizontal transport in the layer, there is convection in the node area of a kink.

The effect of micro-ramp control on fully developed turbulent flow over a forward-facing step (FFS) is investigated in a supersonic low-noise wind tunnel at Mach number 3 using nano-tracer planar laser scattering (NPLS) and supersonic particle image velocimetry (PIV) techniques. High spatiotemporal resolution images and the average velocity profiles of supersonic flow over the FFS with and without the control of the micro-ramps are captured. The fine structures of both cases, including the coherent structures of fully developed boundary layer and the large-scale hairpin-like vortices originated from the micro-ramps as well as the interaction of shock waves with the large-scale structures, are revealed and compared. Based on the time-correlation images, the temporal and spatial evolutionary characteristics of the coherent structures are investigated. It is beneficial to understand the dynamic mechanisms of the separated flow and the control mechanisms of the micro-ramps. The size of the separation region is determined by the NPLS and PIV. The results indicate that the control of the micro-ramps is capable of delaying the separation and diminishing the extent of recirculation zone.

Recent experiments have observed magnetic reconnection in laser-produced high-energy-density (HED) plasma bubbles. We perform two-dimensional (2-D) particle-in-cell (PIC) simulations to investigate magnetic reconnection between two approaching HED plasma bubbles. It is found that the expanding velocity of the bubbles has a great influence on the process of magnetic reconnection. When the expanding velocity is small, a single X line reconnection is formed. However, when the expanding velocity is sufficiently large, we can observe a plasmoid in the vicinity of the X line. At the same time, the structures of the electromagnetic field in HED plasma reconnection are similar to that in Harris current sheet reconnection.

Spatial characterization of a femtosecond laser pulse filament in air is experimentally investigated by detecting the optical emission spectroscopy of laser-induced plasmas. It is shown that the intensity of N I spectral lines have different angular distributions along the filament and the calculated results fit the experimental data well. The obtained degree of atomic polarization along the filament strongly depends on the electron density and the propagation characteristic of the femtosecond laser pulse.

In situ high-pressure x-ray absorption fine structure (EXAFS) measurements on the Zn K-edge in zincblende ZnS are performed up to 31.7 GPa at room temperature using a synchrotron radiation x-ray re-focused by a polycapillary half-lens in the classic energy-scanning transmission mode. The present XAFS data illustrate that ZnS undergoes a phase transition from zincblende F43m to rocksalt Fm3m at 16.9 GPa, accompanied by the increase of the first shell coordination number of the absorption zinc atoms and the unit-cell volume collapse of ～14%. The isothermal equation of state of the F43m ZnS is well presented by the third-order Birch–Murnaghan equation of state with V₀=158.6±0.8 ?³, B₀=87±5 GPa and B₀'=4 (fixed). The high-pressure behavior of ZnS from the XAFS spectra is consistent with the previous high-pressure XRD results. In addition, the present experimental method demonstrates that the large divergent x-ray micro-beam induced by a polycapillary half-lens can suppress effectively the glitches from single crystal diamond anvil and improve significantly the quality of the XAFS data, which will shed light on the high-pressure XAFS applications.

The good quality of 200 pairs of highly strained In_0.24GaAs/GaAs multi-quantum-well (MQW) structure is demonstrated by the x-ray diffraction and photoluminescence curves. Large-area modulators based on the pseudomorphic In_0.24GaAs/GaAs MQW are designed and fabricated successfully, where the diameters are not less than 3 mm and the working wavelength is extended to 1064 nm. The single pass modulation depth is demonstrated to be 0.34 at 1064 nm at a reverse voltage of 80 V .

The operation mechanism of single cross slip multiplication (SCSM) is investigated by studying the response of one dislocation loop expanding in face-centered-cubic (FCC) single crystal using three-dimensional discrete dislocation dynamic (3D-DDD) simulation. The results show that SCSM can trigger highly correlated dislocation generation in a short time, which may shed some light on understanding the large strain burst observed experimentally. Furthermore, we find that there is a critical stress and material size for the operation of SCSM, which agrees with that required to trigger large strain burst in the compression tests of FCC micropillars.

Hydrogen atoms are electrochemically introduced into commercial martensitic T91 steel, and the hydrogen dynamic behaviors are investigated by internal friction (IF) technology. A complex spectrum with multicomponent peaks is detected in the hydrogen-charged T91 steel in the temperature range of 135–290 K. Analysis of peak configuration reveals that the multicomponent peaks consist of one relaxational peak and two non-relaxational peaks. The mechanism of the wide relaxational component is ascribed to the combination of a hydrogen Snoek-like diffusion process and the interaction of hydrogen with movable dislocations, while the two non-relaxational peaks are preliminarily suggested to be caused by some kinds of transient processes related with hydrogen redistribution and outgassing. The binding energy of hydrogen to dislocation is determined to be about 0.19 eV.

Cupric oxide (CuO) nanoparticles were grown on zinc oxide (ZnO) nanorod (NR) arrays to form ZnO–CuO corn-like composites via a simple two step solution-based method. First, ZnO nanorods were grown on a glass substrate by the hydrothermal method. Afterwards, CuO crystals were photochemically deposited on ZnO NRs using ultraviolet (UV) light irradiation at room temperature. The density and size of CuO nanoparticles (NPs) on ZnO NRs can be controlled by the irradiation time of UV light. The structural and optical properties of ZnO–CuO nanocomposites were characterized by using various techniques such as UV-vis absorption spectroscopy, photoluminescence, scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction. ZnO–CuO nanocomposites show an excellent improvement in photocatalytic characteristics compared to bare ZnO NRs.

A cell dynamics simulation is performed for a diblock-diblock copolymers mixture confined between parallel walls. Much richer morphologies are observed in the mixture than in pure diblock copolymers. Multiple novel morphological transitions occur by changing the wall-block interaction and the distance between walls (confinement degree), and both perpendicular and parallel multilayered sandwich structures are obtained in the mixture.

Motivated by the experimental result of an electronic circuit element "fractor", we introduce the concept of a dynamic-order fractional dynamic system, in which the differential-order of a fractional dynamic system is determined by the output signal of another dynamic system. The concept offers an explanation for the physical mechanism of variable-order fractional dynamic systems and multi-system interaction. The properties and potential applications of dynamic-order fractional dynamic systems are further explored by analyzing anomalous relaxation and diffusion processes.

Laser-induced transverse voltage effect is investigated in c-axis tilted Bi₂Sr₂Co₂O_y thin films coated with a graphite layer by using three different laser sources with wavelength ranging from ultraviolet to near-infrared. Due to the transverse thermoelectric effect, voltage signals are detected when the film surface is irradiated by these three lasers and the voltage sensitivity is enhanced as a result of the increasing light absorption at the graphite layer. This work demonstrates that the graphite can be used as an effective absorption layer for fabrication of light detectors based on the photo-thermo-electric conversion.

Beyond the usual many body perturbation theory, with the eigenfunctional theory, we directly calculate the correlation function produced by the Coulomb interaction of electrons in the equation of one-electron Green function, and give the general expression of the non-local effective interaction potential in a Hartree-type potential, which is absent in all previous many body perturbation theories. This effective interaction potential originates from the quantum many body effect of the system, and it cannot be obtained directly by the usual perturbation expression approach. Moreover, using theoretical models, we demonstrate that this effective interaction potential can be used to characterize the electron correlation strength of the system.

We investigate the transport properties of Dirac fermions through velocity-modulation structures, with the Fermi velocity inside the barriers larger than the one outside. It is shown that the transmission exhibits pseudo-periodicity with the incident angle below the critical transmission angle, but attenuates exponentially in the opposite situation. It is found that in the transmission, (1) the pseudo-periodicity turns to periodicity with suitable modulation; (2) line-type peaks appear in the exponential attenuation region for multiple velocity barriers; (3) peak splitting occurs with the number of the velocity barriers increasing. Some sharp oscillations with the falling-edge slopes close to infinity exist in the conductance profile. These novel transport properties suggest significant potential applications in graphene-based devices.

The transfer matrices for both nonsingular and singular cases are constructed to ensure efficient and accurate numerical computation on the electronic and transport properties of graphene quantum wells and superlattices driven by periodic linear potential. An intuitive interpretation is given for the evolution behavior of the current flowing through the multiple graphene quantum wells/barriers by analyzing the interrelationship among the transmission, bias voltage, incident velocity, and linear potential ranges. The energy minibands and density of states of the graphene superlattices with different periods are also examined by using analytical and numerical methods, showing that the period of superlattices plays a crucial role in energy bands and density of states.

An indium-rich InGaN p-n junction is grown on a strain-relaxed InGaN buffer layer. The results show that the n-InGaN is grown coherently on the buffer layer but the p-InGaN layer exhibits a partial strain relaxation. The fabricated InGaN p-n junction has a low reverse leakage current density on the order of 10^?8 A/cm² within the measured voltage range, and exhibits a wide spectral response due to the presence of band tail states or deep level states which origin from indium composition fluctuation or various defects. The measured peak responsivity at 438 nm is 31 mA/W at zero bias and reaches 118 mA/W at 3 V reverse bias. In addition, the Raman spectra of the p- and n-type InGaN alloys are also analyzed.

The modified Becke–Johnson exchange potential approximation is applied to predict the band structure, optical parameters and electron density of SnMg₂O₄ and SnZn₂O₄. The local density approximation, generalized gradient approximation (GGA), EV-GGA significantly underestimate the direct band gap values compared to modified Becke–Johnson approximation. The band gap dependent optical parameters such as dielectric constant, index of refraction, reflectivity, and optical conductivity are calculated and analyzed. A prominent feature of cation replacement is observed and analyzed for these studied compounds. The replacement of the cation Mg by Zn leads to a significant reduction in the value of band gap and consequently affects its dependant optical parameters. This variation is of crucial importance for device fabrication in different regions of the spectrum.

Fe/Sn-codoped In₂O₃ powders and films are prepared by a vacuum annealing process and a pulsed laser deposition technique, respectively. The structural and magnetic properties of the samples are investigated. The obvious room-temperature ferromagnetism is observed in both (In_0.92Fe_0.05Sn_0.03)₂O₃ powders and films, but their magnetic behaviors are very different. The ferromagnetism of the vacuum-annealed powders is partially due to precipitated Fe₃O₄ impurity. By contrast, the ferromagnetism of the films is intrinsic and does not originate from any magnetic impurity, as confirmed by the extensive x-ray absorption spectroscopy and magnetization studies.

A Ba_0.8Sr_0.2TiO₃/CoFe₂O₄ layered heterostructure film was grown on a Pt/TiO₂/SiO₂/Si substrate by rf-magnetron sputtering. X-ray diffraction shows that the film consists of perovskite Ba_0.8Sr_0.2TiO₃ and spinel CoFe₂O₄ phases. The microstructures of the film were observed by a scanning electron microscope (SEM), showing good surface morphology and clear interfaces among the Ba_0.8Sr_0.2TiO₃ film, the CoFe₂O₄ film and the substrate. The variations of dielectric properties with frequency of the heterostructure film are investigated. The heterostructure film simultaneously displays distinct ferroelectricity and ferromagnetism. Moreover, an obvious magnetoelectric coupling effect was observed in the heterostructure film with a maximum magnetoelectric voltage coefficient of 5.0 mV?cm^?1Oe^?1, which is about seven times larger than that of the Ba_0.8Sr_0.2TiO₃/CoFe₂O₄ particulate composite ceramics in a previous report.

We numerically investigate the magnetoelastic (ME) instability in spin 1/2 antiferromagnetic rings with nearest-next neighbor (NNN) coupling J₂ and Dzyaloshinskii–Moriya (DM) interaction D_z. It is found that, for a given D_z, there exists a critical J₂^c . As J₂=J₂^c , the ME instability is irrelative to the DM interaction and NNN coupling. These results may come from the competition between the DM interaction and NNN coupling. The DM interaction does not affect the critical behavior at the point of J₂=0.5, at which the systems always locate in the dimerized state.

Theoretical studies of the cubic perovskite CaFeO₃ are performed using the full potential linearized augmented plane-wave method with GGA+U. The calculated structural parameters are consistent with the experimental results. The tolerance factor reveals the cubic phase of the compound. The spin polarized electronic band structures and densities of states as well as the integer value of the magnetic moment of the unit cell (4μ_B) demonstrate that CaFeO₃ is half metal. Ferromagnetism in CaFeO₃ is due to Fe⁺4–O²–Fe⁺4 superexchange interaction. The robust properties of the compound show that with their compression up to a certain critical lattice constant, known as the robust transition lattice constant, an abrupt change in the electronic and magnetic properties occurs; the compounds lose their integer magnetic moment and become metallic.

We propose and investigate a metal oxide heterostructure (MOH) based resistive switching (RS) device. The driving mechanism of resistive switching (RS) in an MOH is more directly related to oxygen ion/vacancy migration around their interface. The performance of an MOH-based RS device depends on the oxygen mobility, oxygen vacancy concentration as well as its relation to the resistivity. An enhanced ratio of high resistance state to low resistance state can be achieved if the two involved metal oxides are mutually complemental metal oxides in which one of them has larger resistivity with increasing concentration of vacancy while the other one is the reverse.

Precise measurements of the piezoelectric signals are essential for tailoring the properties of ZnO nanowire (NW) based energy conversion devices. We characterize three-dimensional piezoelectric potential profiles of NW arrays using a kelvin probe force microscope (KPFM). A specific device composed of vertically aligned ZnO NWs and thermal responsive polymers is designed for the KPFM test to eliminate surface roughness influence and to avoid mechanical vibrations. The KPFM images show increasing contrasts between the NW and polymer area with the rising temperature, revealing the accumulation of piezoelectric charges. The piezoelectric signals measured by KPFM are around 10 times larger than those measured using external electric circuits.

Using the first principle method, we investigate the influence of Sr/Ti ratio on the atomic structure and dislocation behavior of Sr_n+1Ti_nO_3n+1(Ruddlesden–Popper phase) and Sr_nTi_n+1O_3n+2(Magnéli phase). A linear lattice expansion versus the Sr/Ti ratio exhibits in the Ruddlesden–Popper and Magnéli phases. The Ruddlesden–Popper phase has lower formation energy and superior structural stability than the Magnéli phase. The two phases show different dislocation behaviors and it is found that a possibly preferred slip system <110> {110} emerges in the two phases, and the dislocations are more likely to dissociate into partial dislocations in Magnéli phases.

In order to the modify electron transport property of a metal-semiconductor nanowire(NW)-metal (M-S-M) nanostructure, the effect of high-energy electron irradiation on the current-voltage (I–V) characteristics of M-S-M nanostructure is investigated by in situ transmission electron microscopy. Experimentally measured I–V characteristics of an M-S-M nanostructure can be obviously modified under electron beam irradiation. The current increases rapidly due to increase of the carrier densities resulting from the electron-hole pair excitation in the NW irradiated by the electron beam. If the electron beam is focused on the NW (M-S) nanocontact, the electrons in the Au electrode are excited to higher energy states above the height of the Schottky barrier that becomes transparent to the conduction electrons. As a result, the nonlinear to linear I–V characteristics can be observed. The experimentally revealed I–V characteristics corresponding to transformation from the rectification to Ohm strongly suggest that the intrinsic transport property of the M-S nanocontact can be completely modified by irradiation of the high-energy electron beam.

We systematically investigate the mean pressure measurements at the bottom of a giant static granular column. If a constant overload is placed on top of the bed, the pressure observed displays linearity in overload and non-monotonic in column height. This result is in contradiction with the classical Janssen model. However it is in good agreement with the oriented stress linearity (OSL) model which reveals a local, linear relation between stress components. We conclude that the OSL model works well not only in a tiny static granular column but also in a giant static granular column.

Single and double layers of non-close-packing silica colloidal crystals are prepared using the self-assembly and chemical etching methods. A modulation of size reduction of 21% of silica particles is reported while sustaining the ordering of the structures. As a result of the coupling between light and the two-dimensional (2D) photonic structures, several dips are clearly observed in the measured optical transmission spectra. With decreasing the dielectric particle size, the transmission dips undergo blue shifts and simultaneously become deep. The measured transmission spectra are in good agreement with the theoretical calculations by taking the energy dissipation of the semi-infinite dielectric substrate for the 2D photonic crystals.

InAs quantum dots are introduced into resonant tunneling diodes to study the electronic transport behavior, and a wide bistability (ΔV～0.8 V) is observed in the negative differential resistance region. Based on an analytic model, we attribute the observed distinct bistability of a resonant tunneling diodes with quantum dots to the feedback dependence of energy of the electron-storing quantum dots on the tunneling current density. Meanwhile, we find that this wide bistable region can be modulated sensitively by light illumination and becomes narrower with increasing light intensity. Our results suggest that the present devices can be potentially used as sensitive photodetectors in optoelectronic fields.