The nonlinear Schr?dinger equation is proved to be consistent-tanh-expansion (CTE) solvable. Some types of dark soliton solutions dressed by cnoidal periodic waves are obtained by means of the CTE method.

A hierarchy of new nonlinear evolution equations associated with a 3×3 matrix spectral problem with four potentials is proposed, in which two typical members are a new coupled Burgers equation and a new coupled KdV equation. The bi-Hamiltonian structures for the hierarchy of nonlinear evolution equations are established by using the trace identity.

The Gardner equation is one of the most important prototypic models in nonlinear physics. Many scholars pay much attention to the Gardner equation and various nonlinear excitations of the Gardner equation have been found by many methods. However, it is very difficult to find interaction solutions among different types of nonlinear excitations. In this work, with the help of the Riccati equation, the Gardner equation is solved by the consistent Riccati expansion. Furthermore, we obtain the soliton-cnoidal wave interaction solutions of the Gardner equation.

We investigate the single-photon transport properties in a one-dimensional coupled-resonator waveguide non-locally coupled to a whispering-gallery resonator embedded with two separated two-level atoms based on the real-space approach. The control of single-photon transport is realized by modulating the detuning between two separated atoms, phase differences, and the symmetric/asymmetric nonlocal couplings. The multi-frequency photon-filter is obtained, and the influences of dissipation effects on single-photon transmission spectra and the phase shift are also discussed.

Although some ideal quantum key distribution protocols have been proved to be secure, there have been some demonstrations that practical quantum key distribution implementations were hacked due to some real-life imperfections. Among these attacks, detector side channel attacks may be the most serious. Recently, a measurement device independent quantum key distribution protocol [Phys. Rev. Lett. 108 (2012) 130503] was proposed and all detector side channel attacks are removed in this scheme. Here a new security proof based on quantum information theory is given. The eavesdropper's information of the sifted key bits is bounded. Then with this bound, the final secure key bit rate can be obtained.

By virtue of the thermo-entangled states representation of the density operator and using the dissipative interaction picture, we solve the master equation of a driven damped harmonic oscillator in a squeezed bath. We show that the essential part of the dynamics can be expressed by the convolution of the initial Wigner function with a special kind of normalized Gaussian in the phase space and relate the dynamics with the change of Gaussian ordering of the density operator.

We present an alternate adiabatic evolution for the Deutsch–Jozsa problem. The biggest difference of our adiabatic evolution constructed here with those appearing before is that an alternate initial Hamiltonian is used for the adiabatic evolution, with which the evolution task can be finished in O(1) time complexity. Our construction mostly resembles the one discussed by Das et al. [Phys. Rev. A 65 (2002) 062310], except for the initial system Hamiltonian of the adiabatic algorithm.

We deal with Einstein's field equations with a time-decaying cosmological term of the forms (i) Λ = β(ä/a) + α/a² and (ii) Λ = α/a², where a is the average scale factor of the universe, α and β are constants for a spatially homogeneous and anisotropic LRS Bianchi type-II spacetime. Exact solutions of the field equations for stiff matter are obtained by applying a special law of variation for the Hubble parameter. Anisotropic cosmological models are presented with a constant negative deceleration parameter which corresponds to the accelerated phase of the present universe. The cosmological constant Λ is obtained as a decreasing function of time that is approaching a small positive value at the present epoch, which is corroborated by the consequences from recent supernovae Ia observations. The physical and kinematical behaviors of the models are also discussed.

Effects of spike frequency adaptation (SFA) on the synchronous behavior of population neurons are investigated in electrically coupled networks with a scale-free property. By a computational approach, we corroborate that pairwise correlations between neurons would decrease if neurons exhibit the feature of SFA, which is similar to previous experimental observations. However, unlike the case of pairwise correlations, population activities of neurons show a rather complex variation mode: compared with those of non-adapted neurons, neurons in the networks having weak-degrees of SFA will impair population synchronizations; while neurons exhibiting strong-degrees of SFA will enhance population synchronizations. Moreover, a variation of coupling strength between neurons will not alter this phenomenon significantly, unless the coupling strength is too weak. Our results suggest that synchronous activity of electrically coupled population neurons is adaptation-dependent, and this adaptive feature may imply some coding strategies of neuronal populations.

We develop an equivalence between the diagonal slices and the perpendicular slices of 3D Young diagrams via Maya diagrams. Furthermore, we construct the fermion representation of quantum toroidal algebra on the 3D Young diagrams perpendicularly sliced.

We investigate the 2- and 3-state ferromagnetic Potts models on the simple cubic lattice using the tensor renormalization group method with higher-order singular value decomposition (HOTRG). HOTRG works in the thermodynamic limit, where we use the Z_q symmetry of the model, combined with a new measure for detecting the transition, to improve the accuracy of the critical point for the 2-state model by two orders of magnitude, obtaining T_c=4.51152469(1). The 3-state model is far more complex, and we improve the overall understanding of this case by calculating its thermodynamic quantities with high accuracy. Our results verify that the first-order nature of the phase transition and the HOTRG transition temperature benchmarks the most recent Monte Carlo result.

A dimensional artifact is developed, which is a chromium (Cr) deposition grating fabricated by a laser-focused atomic deposition technique. The mean pitch of the grating is measured by using a metrological atomic force microscope with a large range, where a series of reference signs have been performed to locate the deposition area. Cosine error of the measurement result is analyzed and eliminated by the iterative angle calibration. The measurement result shows that the mean pitch of the grating is 212.66 ± 0.02 nm, which is very close to half of the standing laser wavelength (λ=425.55 nm). This means that the grating has traceability with high accuracy and can substitute the laser interference technology for instrument calibration. Moreover, using the Cr deposition grating as a nano standard can shorten the traceability chain and improve the practical application.

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 U_πν(5)–O_πν(6) transition and towards U_πν(5) symmetry. The key sensitive quantities of the B(E2) branching ratio clearly indicate that ¹⁰²Ru is a primary O_πν(6) symmetry, while with a somewhat U_πν(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 propose three parameter sets for the Lagrangian with nonlinear derivative couplings in the relativistic mean field theory. The properties of finite nuclei and nuclear matter are explored. The study shows that a good description of binding energies, charge radii and neutron skin thickness of nuclei is achieved with this Lagrangian. It is also shown that this Lagrangian model leads to a softening of the equation of state and symmetry energy at high densities, and gives a much less repulsive optical potential at high nucleon energies compared to standard relativistic mean field models.

In heavy ion collision, the event plane is a key parameter defined as the plane composted by the impact parameter b and beam axis z. It is a crucial reference for various observables, which focus on the initial spatial anisotropy of the overlap region in heavy ion collision. We notice that in some recent heavy ion collision experiments, due to potentially inefficient or even the invalidity of experimental facilities, the reconstructed event plane, which is used in elliptic flow study, may be biased towards a non-flat distribution. In this study, we develop a toy model for fast estimation of the bias effect and its influence on the elliptic flow. The possible azimuthal bias of the detector is firstly studied by varying the part of its azimuthal information. We also study on the limit acceptance of the detector, which will be used to measure the particle of interest in an elliptic flow. The outcomes are presented by comparing the flow study results with or without the non-flat effect on the event plane.

Thanks to its noteworthy mechanical properties, excellent damage tolerance and good thermal stability, the Ti₃SiC₂ ternary compound has attracted great concern and has been considered as a potential structural component material for the 4th generation of reactors (e.g., gas fast nuclear reactors) and future fusion reactors. The outstanding properties are due to the nanolamellar structure which imparts characteristics of both metals and ceramics to this material. In our work, Ti₃SiC₂ samples have been irradiated by C⁺ ions with a high fluence of 1.78×10¹⁷ ions/cm² at a range of temperatures from 120°C–850°C. Subsequently, series of characterization techniques including synchrotron irradiation x-ray diffraction, scanning electron microscopy and nano-indentation are carried out to understand the changes of microstructure and mechanical properties. The composition exhibits high damage tolerant properties and a high recovery rate through the analysis, especially at high temperature. The minimum damage to an irradiated sample appears around 350°C in the temperature range 120°C–550°C. At a high irradiation temperature, a significant reduction in the damage can be achieved and an almost complete lack of damage compared with an un-irradiated sample is revealed at the temperature of 850°C.

Advantages of using the artificial neural network method in neutron spectra unfolding are investigated in comparison with the maximum entropy unfolding method. By introducing the information entropy theory, we find that for the spectrum with the information entropy over 3.5, the four-layer feed-forward neural network (11-35-55-60) and the maximum entropy method generally demonstrate the same unfolding performance, while the spectrum with the information entropy lower than 3.5, the artificial neural network unfolding model is recommend due to the fact that the artificial neural network method has a stronger negative correlation between the entropy of the spectra and the mean squares error of the spectra than the maximum entropy method.

A blue emitting phosphor Sr₃Bi(PO₄)₃:Eu²⁺ is synthesized by a high-temperature solid state method, and its luminescent property is investigated. Sr₃Bi(PO₄)₃:Eu²⁺ can create blue emission under the 332 radiation excitation, and the prominent luminescence in blue (423 nm) due to the 4f5d¹→4f⁷ transition of the Eu²⁺ ion. The crystallographic sites of the Eu²⁺ ion in Sr₃Bi(PO₄)₃ are analyzed, and the 420 and 440 nm emission peaks of the Eu²⁺ ion are assigned to the nine-coordination and eight-coordination, respectively. The emission intensity of Sr₃Bi(PO₄)₃:Eu²⁺ is influenced by the Eu²⁺ doping content, and the concentration quenching effect is observed. The quenching mechanism is the dipole-dipole interaction, and the critical distance of energy transfer is calculated by the concentration quenching method to be approximately 1.72 nm.

The temperature of the remaining cold ⁸⁷Rb atoms confined in a vapor cell magneto-optical trap after two-step photoionization has been measured. In the two-step photoionization process, the first excitation laser is served by the cooling laser and the second excitation laser is served by a continuous semiconductor laser with a wavelength of 450 nm. The results show that the temperature of the remaining cold atoms decreases as the intensity of the second excitation laser increases. Moreover, the relationship between the temperature T and number N of the remaining cold atoms generally follows a power law, while it deviates from the well-known T∝N^1/3 and the power factor is smaller than 1/3. We propose that ion-atom collisions occurring during a photoionization process strongly influence the temperature scaling law in an optically dense magneto-optical trap in the presence of an ionization laser. In addition, the forced evaporative cooling due to the combined effect of the detuning of the first excitation laser and the two-step photoionization plays a role in cooling the remaining cold atoms and results in the dependence of the power factor on the detuning of the first excitation laser.

The Faraday rotation of weak linearly polarized probe light is observed as it passes through a sample of cold ⁸⁷Rb atoms prepared by diffused light in an integrating sphere. The rotation angle of the probe light-polarization as functions of laser intensity, detuning and biased magnetic field is measured. A Ramsey fringe with a linewidth of 35 Hz and contrast up to 92% is demonstrated. This method has potential applications in improving the performance of atomic clocks with cold atoms.

On the basis of the vectorial Rayleigh diffraction integral, the analytical expressions for the electric fields of cylindrical vector vortex beams (CVVBs) with an arbitrary polarization order in the far-field are derived, which helps us investigate the far-field properties of the CVVBs in the non-paraxial and paraxial regimes. Some detailed comparisons of the non-paraxial results with the paraxial results are made, which show that the polarization order and the ratio of beam waist width to wavelength play an important role in determining the non-paraxiality of CVVBs. In addition, the polarization order and the ratio of beam waist width to wavelength have a great impact on the diffraction effect and the divergent behavior of CVVBs in the far-field.

A passively Q-switched Nd YAG eye-safe laser operating at 1444 nm with graphene as a saturable absorber is reported. Under a pump power of 23.7 W, the maximum average output power, minimum pulse width, pulse repetition rate and single pulse energy are 411 mW, 560 ns, 85 kHz, and 4.83 μJ, respectively. This is the first demonstration of a Nd:YAG eye-safe laser passively Q-switched by graphene.

We demonstrate the continuous wave p-polarized single longitudinal mode (SLM) operation of an Er:YAG laser at 1617.6 nm pumped by a diode-laser with three inserted Fabry–Perot (FP) etalons at room temperature. The Brewster angle inserted FP is applied to obtain the p-polarized laser. For free running, the maximum output power is 570 mW with a pump power of 12.5 W. An incident pump power of 12.5 W is used to generate the maximum p-polarized single longitudinal mode output power of 78.5 mW, corresponding to a slope efficiency of 1.6% and an optical-to-optical efficiency of 0.61%. The beam quality M² is measured to be 1.15 at the highest SLM output power. This stable polarized SLM oscillation is encouraging due to its application for an injection-locked system used as a master laser.

A high power diode-pumped diffusion-bonded Tm:YLF laser operating at 1889.5 nm with a FWHM linewidth of less than 0.1 nm is reported. A Brewster plate and two Fabry–Perot etalons are inserted in the laser cavity for spectral narrowing and stabilization. Under an incident pump power of 136.8 W, 46.1 W of output power is achieved, corresponding to an optical-to-optical conversion efficiency of 33.7% and a slope efficiency of 42.8%. The laser wavelength shift of only 0.07 nm with the incident pump power from 20.1 W to 136.8 W is observed. The M² factor at maximum output power is calculated to be 2.3 in the x-axis and 2.0 in the y-axis, respectively.

A 2.09-μm in-band pumped passively Q-switched Ho:YAG laser is demonstrated. Single layer graphene deposited on a quartz substrate is used as the saturable absorber for the Q-switched operation. The minimum pulse width of 2.11 μs is obtained at an average output power of 100 mW, corresponding to a pulse repetition frequency of 57.1 kHz and the pulse energy of 1.75 μJ. The beam quality factors M² of the Q-switched laser are 1.18 and 1.22 in the horizontal and longitudinal direction, respectively. The optical-to-optical conversion efficiency of the passively Q-switched laser is 4.3%, which is the highest conversion efficiency in the 2 μm wavelength, to the best of our knowledge. It shows clearly that the Ho:YAG crystal is a potential gain medium in the 2 μm range for the graphene application.

A 16-channel distributed-feedback (DFB) laser array with a monolithic integrated arrayed waveguide grating multiplexer for a wavelength division multiplex-passive optical network system is fabricated by using the butt-joint metal organic chemical vapor deposition technology and nanoimpirnt technology. The results show that the threshold current is about 20–30 mA at 25°C. The DFB laser side output power is about 16 mW with a 150 mA injection current. The lasing wavelength is from 1550 nm to 1575 nm covering a more than 25 nm range with 200 GHz channel space. A more than 55 dB sidemode suppression ratio is obtained.

We present an experimental study of a continuous-wave Nd:YVO₄ laser diode-pumped directly in band at 880 nm. By using a compact positive confocal unstable-stable hybrid resonator, a maximal laser output of 170 W at 1064 nm is realized. The slope efficiency and optical-to-optical efficiency are 56.7% and 51.3%, respectively. The M² factors in the unstable direction and in the stable direction they are 1.9 and 1.3, respectively.

Sol-gel TiO₂ films are prepared by the dip-coating method and the spin-coating method, and then annealing is performed at different temperatures. The structures, optical properties, surface morphologies, absorption and laser-induced damage threshold (LIDT) at 1064 nm and 12 ns of the films are investigated. The results show that the dip-coating method can be used to obtain a higher LIDT than the spin-coating method. When the annealing temperature increases from 80°C to 120°C, the dip-coated film obtains a higher LIDT, whereas the spin-coated film obtains a lower LIDT. In addition, the damage morphology is a spalling pit for the dip-coated film annealed at 80°C. When the annealing temperature increases to 120°C, it shows a melting area. For both the spin-coated films annealed at different temperatures, the damage morphologies are the combination of spalling and melting. The differences in LIDT and damage morphologies of the films are discussed.

An intracavity frequency doubling electro-optically Q-switched Nd:YLF 523.5 nm laser is developed. An appropriate cylindrical lens is employed in the oscillator to optimize the mode size and to improve the stability of the cavity. With an incident pump pulse energy of 58 mJ at a 500 Hz repetition rate, a green pulse energy of 16.8 mJ at 523.5 nm is obtained, corresponding to an optical-optical conversion efficiency of 29%. The pulse width is less than 8 ns, and the beam quality factor is M²≤2.5.

The 885 nm direct pumping method, directly into the ⁴F_3/2 emitting level of Nd³⁺ ion, is used to a Nd:CNGG crystal to product passive Q-switched 1061 nm laser pulses, for the first time to the best of our knowledge. A maximum average output power of 1.16 W for 1061 nm Q-switched pulses and a repetition rate of 12.54 kHz are obtained. The pulse width is measured to be 24 ns and the peak power is 3.843 kW. A high-quality fundamental transverse mode can be observed owing to the reduction of the thermal effect for Nd:CNGG crystal by 885 nm direct pumping.

We report the novel dynamic of 3D dissipative vortices supported by an umbrella-shaped potential (USP) in the 3D complex Ginzburg–Landau (CGL) equation with the cubic-quintic nonlinearity. The stable solution of vortices with intrinsic vorticity S=1 and 2 are obtained in the 3D CGL equation. An appropriate USP forces the vortices continuously to throw out fundamental 3D solitons (light bullets) along the folding umbrella. The dynamic regions of the strength of the potential with the changing number of folding umbrella are analyzed, and the rate of throwing increases with the strength of the potential. A weak potential cannot provide vortices with enough force. Then, the vortices will be stretched into polygons. However, a strong potential will destroy the vortices.

A photoacoustic system with an annular transducer array is presented for rapid, high-resolution photoacoustic tomography of animals. An eight-channel data acquisition system is applied to capture the photoacoustic signals by using multiplexing and the total time of data acquisition and transferring is within 3 s. A limited-view filtered back projection algorithm is used to reconstruct the photoacoustic images. Experiments are performed on a mouse head and a rabbit head and clear photoacoustic images are obtained. The experimental results demonstrate that this imaging system holds the potential for imaging the human brain.

The similarity law of gas discharge is not always valid due to the occurrence of some elementary processes, such as the stepwise ionization process, which are defined as the forbidden processes. To research the influence of forbidden processes on the similarity law, physical parameters (i.e., the electric field, electron density, electron temperature) in similar gaps are investigated based on the fluid model of gas discharge. The products of gas pressure p and dimensions are kept to be constant in similar gaps and the discharge model is solved with and without the forbidden processes, respectively. Discharges in similar gaps are identified as glow discharges and the typical similarity relations all are investigated. The results show that the forbidden processes cause significant deviations of similarity relations from the theoretical ones and the deviations are enlarged as the scaled-down factor k increases. If the forbidden processes are excluded from the model, the similarity law will be valid in argon glow discharge at low pressure.

Ultrashort 10²²–10²⁴ W/cm² laser pulses will offer the possibility of producing monoenergetic electron beams in the GeV–TeV level in the future. A laser-electron acceleration scheme is proposed by the interaction between a thin solid foil and an ultra-intense laser pulse for a₀≥800σ₀, where a₀ is the normalized laser field and σ₀ is the normalized plasma surface density. The energy of the electrons as a function of time can be described by a simple model which indicates that an exponential relationship exists between the energy and the normalized time τ. A quasi-monoenergetic high density electron beam with 1.3 GeV energy and a 2.2% energy spread has been predicted for a₀=223.5 by particle-in-cell simulations. Characteristics of the ultra-high density electron layer formed in the early period of the acceleration are discussed.

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.

Comprehensive first-principle calculations on strained SnO₂ crystal structure indicate that the formation energy of different types of oxygen vacancies depends on the external strain. Many novel Raman modes can be observed, their intensities and positions are strongly dependent on applied stain, which can be ascribed to crystal symmetry destruction by oxygen vacancies. Applied strain can compress/stretch distances between Sn and O atoms; therefore, Sn–O band vibration frequencies can be adjusted accordingly. Our calculated results disclose that the Raman spectra of SnO₂ crystal structure with different types of oxygen vacancies are obviously different, which can be used to identify the oxygen vacancy types in strained SnO₂ crystal structures.

The most basic local conversion is local operations and classical communications (LOCC), which is also the most natural restriction in quantum information processing. We investigate the conversions between the ground states in quantum critical systems via LOCC and propose a novel method to reveal the different convertibilities via majorization relation when a quantum phase transition occurs. The ground-state local convertibility in the one-dimensional transverse field Ising model is studied. It is shown that the LOCC convertibility changes nearly at the phase transition point. The relation between the order of quantum phase transitions and the LOCC convertibility is discussed. Our results are compared with the corresponding results by using the Rényi entropy and the LOCC convertibility with assisted entanglement.

Large thermal expansion at room temperature and high phase transition temperature of ZrV₂O₇ limit its practical applications and are reduced by the high solubility of hetero-valence ion (Cu²⁺) on the basis of an equal-valence substitution of P⁵⁺ for V⁵⁺. The temperature-dependent Raman spectra show that Zr_0.9Cu_0.1V_1.6P_0.4O_6.9 maintains a normal parent cubic structure till 173 K and transforms to a 3×3×3 cubic superstructure below 173 K. Temperature dependent x-ray diffraction patterns of Zr_0.9Cu_0.1V_1.6P_0.4O_6.9 show near zero and negative thermal expansion. High solubility of lower valence Cu²⁺ relates to an equal-valence substitution of smaller P⁵⁺ for V⁵⁺, which extends the bond angle of V(P)–O–V in ZrV_1.6P_0.4O₇ close to 180°. The change of microstructure is considered to be responsible for reduced phase transition temperature and thermal expansion.

We develop a non-volatile resistive switching device in a Si–SiO₂–Mg structure with an on/off ratio of about 4.5 at a certain transition voltage after being stimulated by a large current. It is observed that the resistance transition voltage V_t shifts reproducibly under a reversed large current. By applying a reading voltage in the range of V_t, non-volatile resistive switching phenomena with an endurance of more than 80 cycles are observed. Moreover, it is also found that the magnetic field could shift V_t to higher values, yielding a voltage dependent room-temperature magnetoresistance in the range of 10³% at 1 T. The multifunctional properties of the silicon device suggested by this work may be beneficial to the silicon based industry.

We report the growth of a-plane InN on an r-plane sapphire substrate by plasma-assisted molecular-beam epitaxy. It is found that the a-plane InN is successfully grown by using a GaN buffer layer, which has been confirmed by reflection high-energy electron diffraction, x-ray diffraction and Raman scattering measurements. The Hall effect measurement shows that the electron mobility of the as-grown a-plane InN is about 406 cm²/V?s with a residual electron concentration of 5.7×10¹⁸ cm^?3. THz emission from the a-plane InN film is also studied, where it is found that the emission amplitude is inversely proportional to the conductivity.

We carefully investigate the transport and capacitance properties of few layer charge density wave (CDW) 2H–TaS₂ devices. The CDW transition temperature and the threshold voltage vary from device to device, which is attributed to the interlayer interaction and inhomogeneous local defects of these micro-devices based on few layer 2H–TaS₂ flakes. The nonlinear rather than linear current voltage characteristic of 2H–TaS₂ devices is observed in our experiment at low temperature. The temperature dependence of the relative threshold voltage can be scaled to (1?T/T_r)^0.5+δ with δ=0.08 for the different measured devices with the presence of the CDWs. The conductance-voltage and capacity-voltage measurements are performed simultaneously. At very low ac active voltage, we find that the hysteresis loops of these two measurements exactly match each other. Our results point out that the capacity-voltage measurements can also be used to define the threshold depinning voltage of the CDW, which gives us a new method to investigate the CDWs.

Two correlated superconducting phases are identified in the layered superconductor BaTi₂(Sb_1?xBi_x)₂O (x=0.16), with the superconducting transition temperatures of T_C=6 K (the high T_C phase) and 3.4 K (the low T_C Phase), respectively. The 6 K superconducting phase appears first in the as-prepared sample and can decay into the low T_C phase by exposure to an ambient atmosphere for a certain duration. Specially, the high T_C phase can reappear from the decayed sample with the low T_C phase by vacuum annealing. It is also found that the CDW/SDW order occurs only with the 6 K superconducting phase. These notable features and alteration of the superconductivity due to the post-processing and external pressure can be explained by the scenario of electronic phase separation.

Dielectric and ferroelectric characteristics for Pb_1?xBa_x(Fe_1/2Nb_1/2)O₃ (x=0, 0.05, 0.1, 0.15, and 0.2) ceramics are determined together with their structures. X-ray diffraction (XRD) analysis confirms the solid solutions with the cubic structure. The dielectric nature changes from diffuse ferroelectric to relaxor ferroelectric with increasing x, while the phase transition temperature T_C (or T_m) decreases monotonously. The diffuse ferroelectric phase transition is observed in the solid solutions with 0≤x≤0.05. For Pb_1?xBa_x(Fe_1/2Nb_1/2)O₃ with 0.1≤x≤0.2, relaxor ferroelectric behavior is determined, and the Vogel–Fulcher equation is used to describe the relaxor behavior. The 1/ϵ versus T plots reveal the diffusion dielectric characteristics in both diffuse and relaxor ferroelectrics.

Ce-doped HfO₂ (HfCeO) films are prepared by radio-frequency magnetron sputtering. The influences of rapid thermal annealing on the structure and electrical properties of HfCeO films are investigated. The results show that the incorporation of Ce into HfO₂ increases the crystallization temperature of HfO₂, and the cubic phase of HfO₂ can be stabilized by incorporating Ce into HfO₂. After high temperature annealing, Hf 4f core level spectra shift to a higher energy, whereas O 1s core level spectra shift to a lower energy. With increasing annealing temperatures, the effective permittivity increases, whereas the flat-band voltage shift and effective oxide charge density decrease. Moreover, the leakage current density of the HfCeO films decreases initially, and then increases as the annealing temperature increases.

The release of bound charges by shock wave loading of poled lead zirconate titanate (PZT 95/5) ferroelectric ceramics can result in a high-power electrical energy output. In this study, a theoretical formulation describing the depolarization and electrical response of porous PZT 95/5 ceramics in the normal mode to shock wave compression loading perpendicular to the polarization direction is developed. The depoling process in porous poled PZT 95/5 ceramics is analyzed by using a parallel circuit consisting of a current source, capacitance, conductance and a circuit load. This modeling takes the effects of porosity on wave velocity and remanent polarization and dielectric constant into account, and the effects of variations in dielectric constant and conductivity in the shocked region are assessed. The output current characteristics of porous PZT 95/5 ceramics under short-circuit and resistive load conditions are analyzed and compared with the experiment, with the results showing that theoretical predictions taking into consideration the porosity of ferroelectric ceramics are in close agreement with the experimentally measured electrical response of porous PZT 95/5 under shock wave compression loading.

A type of planar magnetic metamaterial is proposed with a square winding microstructure as a superlens for magnetic resonance imaging (MRI) applications. A direct magnetic field mapping measurement demonstrates that the radio-frequency magnetic field passing through the superlens is increased by as high as 46.9% at the position of about 3 cm behind the superlens. The resonance frequency of the fabricated slabs is found to be in good agreement with the target frequency (63.6 MHz) for a 1.5 T MRI system. MRI experiments with the magnetic superlens show that the intensity of the image and the SNR (signal-to-noise ratio) are both enhanced, implying promising MRI applications of our planar magnetic superlens.

A CdS:CdO/Si multi-interface nanoheterostructure array (CdS:CdO/Si-NPA) is prepared by a chemical bath deposition method, and three emission bands are observed in the as-grown CdS:CdO film. By measuring its temperature-dependent photoluminescence (PL) spectrum, the variation trends of the peak energies and intensities with temperature for the three bands are obtained. Based on the theoretical analyses and fitting results, the non-radiative recombination processes corresponding to the PL quenching for the three emission bands are attributed to the thermally activated transition between heavy-hole and light-hole levels (at low temperature) and the thermal escape due to the scattering from longitudinal optical phonons (at high temperature), the transition from acceptor levels to surface states, and the transition related to surface defect states, respectively. The clarification of the non-radiative recombination processes in CdS:CdO/Si-NPA might provide useful information for promoting the performance of optoelectronic devices based on CdS/Si nanoheterostructures.

A laser ablation technique is applied for synthesis of silver nanoparticles in different concentrations of polyvinyl alcohol (PVA) aqueous solution. The ablation of high pure silver plate in the solution is carried out by a nanosecond Q-switched Nd:YAG pulsed laser. X-ray diffraction and transmission electron microscopy are implemented to explore the particles sizes. The effects of PVA concentrations on the absorbance of the silver nanoparticles are studied as well, by using a UV-vis spectrophotometer. The preparation process is carried out for deionized water as a reference sample. The comparison of the obtained results with the reference sample shows that the formation efficiency of nanoparticles in PVA is much higher and the sizes of particles are also smaller.

The repeatable bipolar resistive switching phenomenon is observed in amorphous Al₂O₃ prepared by metal-organic chemical vapor deposition on ITO glass, with ITO as the bottom electrode and Ag as the top electrode. The crystal structure, morphology, composition and optical properties of Al₂O₃ thin films are investigated by x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy and ultraviolet-visible-infrared spectroscopy, respectively. The electronic character of Ag/Al₂O₃/ITO structure is tested by an Agilent B1500A. The device shows a typical bipolar resistive switching behavior under the dc voltage sweep mode at room temperature. The variation ratio between HRS and LRS is larger than nearly three orders of magnitude, which indicates the good potential of this structure in future resistive random access memory (ReRAM) applications. Based on the conductive filament model, the high electric field is considered the main reason for the resistive switching according to our measurements.

The structural evolution during the oxidation process of graphite by a modified Hummers method is investigated. The graphite oxide (GO) composition, disorder parameter, and structures are confirmed by means of x-ray diffraction, Fourier transform infrared spectroscopy, Raman, and scanning electron microscope techniques. Results show that: Hydroxyl, carboxyl and ether groups are present in the low-temperature oxide (at 0°C); and the degree of oxidation is increased with a longer oxidation time. The middle-temperature oxidation (35°C) is a transitory stage with a slight change to the GO structures. While for the high-temperature oxidation (95°C), the hydroxyl, carboxyl and epoxide functional groups are largely originated on the GO flakes. Hydroxyl groups are transformed into more epoxide groups with longer oxidation time, and at the same time, ether groups are eliminated, leading to defects (such as holes) on the GO flakes.

We report the structure and magnetic properties of (In,Mn)As based core-shell nanowires grown on Si (111) by molecular-beam epitaxy. Compared to the core InAs nanowire with a flat side facet and consistent diameter, the core-shell nanowire shows a rough sidewall and an inverse tapered geometry. X-ray diffraction, transmission electron microscopy and energy-dispersive x-ray spectroscopy show that (In,Mn)As is formed on the side facets of InAs nanowires with a mixture of wurtzite and zinc-blende structures. Two ferromagnetic transition temperatures of (In,Mn)As from magnetic measurement data are observed: one is less than 25 K, which could be attributed to the magnetic phase with diluted Mn atoms in the InAs matrix, and the other is at ～300 K, which may originate from the undetectable secondary phases such as MnAs nanoclusters. The synthesis of (In,Mn)As based core-shell nanowires provides valuable information to exploit a new type of spintronic nano-materials.

We report dc and the first-ever measured small signal rf performance of epitaxial graphene field-effect transistors (GFETs), where the epitaxial graphene is grown by chemical vapor deposition (CVD) on a 2-inch c-plane sapphire substrate. Our epitaxial graphene material has a good flatness and uniformity due to the low carbon concentration during the graphene growth. With a gate length L_g=100 nm, the maximum drain source current I_ds and peak transconductance g_m reach 0.92 A/mm and 0.143 S/mm, respectively, which are the highest results reported for GFETs directly grown on sapphire. The extrinsic cutoff frequency (f_T) and maximum oscillation frequency (f_max) of the device are 12 GHz and 9.5 GHz, and up to 32 GHz and 21.5 GHz after de-embedding, respectively. Our work proves that epitaxial graphene on sapphire substrates is a promising candidate for rf electronics.

A high-resolution micro-grating displacement sensor with diffraction-based and integrated electrostatic actuation is proposed and experimentally demonstrated. The Al reflecting membrane is fabricated at the bottom of a silicon moving part and the Au micro-gratings are patterned on a transparent substrate. This structure forms a phase sensitive diffraction grating, providing the displacement sensitivity of the micro-grating interferometer. It shows sensitivity adjustment and self-calibration capabilities with electrostatic actuation. Additional system components include a coherent light source, photodiodes, and required electronics. Experimental results show that the displacement sensor has a sensitivity of about 1.8 mV/nm and a resolution of less than 1 nm in the linear region. This displacement sensor is very promising in the fields requiring high sensitivity, broad dynamic range, and immunity to electromagnetic interference.

Phosphosilicate glass (PSG) electrolyte films are deposited by improving the content of phosphorus doping during plasma-enhanced chemical vapor deposition, and a fast electric-double-layer (EDL) polarization response of 100 kHz is measured. The mechanism of the fast polarization response and EDL formation are investigated in detail. By using PSG electrolyte films as gate dielectrics, indium-zinc-oxide (IZO) thin-film transistors (TFTs) are fabricated on flexible plastic substrates. Due to the huge EDL gate capacitance, such TFTs show only 0.8 V operation and excellent electrical performances with a large current on/off ratio of 10⁷, low subthreshold swing of 72 mV/decade and high field-effect mobility of 16.76 cm²/V?s. More importantly, the devices exhibit a fast switching response above 100 Hz. Our results demonstrate that such PSG gated TFTs take a great step for low-power flexible oxide electronics application.

Sb₂Te films with different Ti contents (Ti_xSb₂Te) are derived via the target-attachment method by using the magnetron sputtering technique. The effects of the Ti content on the phase change characteristics and the microstructures are investigated by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy and atom force microcopy. Resistance-temperature measurements are carried out to reveal the enhanced crystallization temperature of Ti_xSb₂Te films, indicating a better thermal stability in such films. Both the activation energy and the temperature for 10 y data retention increase with increasing the concentration of Ti. It indicates that the crystallization of the amorphous Sb₂Te film could be suppressed by the introduction of Ti. The improvement of crystallization temperature and the thermal stability of the amorphous Sb₂Te film results from the introduction of Ti in Sb-Te bond that decreases the binding energy of Sb 4d and Te 4d.

We extend the Achlioptas percolation (AP) process [Achlioptas et al. Science 323 (2009) 1453] to two generalized Achlioptas percolation processes named GAP1 and GAP2. GAP1 induces a weighted probability factor α in the node sampling process and excludes the intracluster links. Based on GAP1, GAP2 requires m pairs of nodes sampled to add m candidate links that should be residing in 2m different clusters at each step. In the evolution of GAP1, the phase transition can evolve from the continuous to the 'most explosive' percolation as the value of the factor α is decreasing to a certain negative number. It indicates that there might be a type of discontinuous transition induced by the probability modulation effect even in the thermodynamic limit, and the most explosive percolation is only one of its extreme cases. We analyze the characteristics of the evolving process of the two-nodes-clusters and the cluster-size distribution at the transformation point for different α; the numerical results suggest that there might be a critical value α₀ and the phase transition should be discontinuous (α≤α₀) or continuous (α>α₀). In the evolution of GAP2, twice phase transitions are observed successively and the time duration between them becomes shorter till they amalgamate into the 'most explosive' percolation. The first transition is induced by the probability modulation effect analyzed in GAP1, the second transition, induced by the three coexisting giant clusters, is always discontinuous and the maximum jump of order parameter approaches N/3 while the value of the factor α is increasing to 1.4 approximately. In this work, two typical discontinuous transitions induced respectively by the probability modulation and the extended local competition are exhibited in GAP2, which might provide references to analyze the discontinuous phase transition in networks further.