We report an extraordinary sound absorption enhancement in low and intermediate frequencies achieved by a thin multi-slit hybrid structure formed by incorporating micrometer scale micro-slits into a sub-millimeter scale meso-slit matrix. Theoretical and numerical results reveal that this exotic phenomenon is attributed to the noticeable velocity and temperature gradients induced at the junctures of the micro- and meso-slits, which cause significant loss of sound energy as a result of viscous and thermal effects. It is demonstrated that the proposed thin multi-slit hybrid structure with micro-scale configuration is capable of controling low frequency noise with large wavelength, which is attractive for applications where the size and weight of a sound absorber are restricted.

We discuss, in terms of a simple model, the spin wave excitations, spontaneous magnetization and response to alternating fields of magnetic superlattices.

We report the superconductivity in iron-based oxyarsenide Sm[O_1-xF_x]FeAs, with the onset resistivity transition temperature at 55.0K and Meissner transition at 54.6K. This compound has the same crystal structure as LaOFeAs with shrunk crystal lattices, and becomes the superconductor with the highest critical temperature among all materials besides copper oxides up to now.

Mo_1-xGe_x, Mo_1-xSi_x, films were prepared by getter sputtering onto liquid nitrogen cooled substrates. The amorphous phase formations were Ge > 22 at . % , Si > 18 at .% respectively. With the increase of Ge, Si content, Tc decreased from 6 to 3K in the amorphous state. The measured results of (dB_c2/dT)T_c , J_c and ρ( 300K) /ρ(8K) indicated that the four chosen Mo_1-xSi_x films exhibit fundamental characteristics of amorphous superconductors.

The structure function for the deep–inelastic scattering of electrons on He, Be, Al, Fe and Au are analysed. It is found that all these structure functions satisfy a kind of scale relation, and the scale parameter ξ_A in creases logarithmically with the nucleon number A.

The high resolution laser spectroscopy study on the l(2, -1) type Coriolis resonance in CH₃Fv₅ R_QO and p_p3 was carried out. An improved value of E₅ is obtained, E₅=2.3892(9) x10^-3cm^-1.

Different α-nucleus potentials for the anomalous large angle scattering have been tested by the ⁴⁰Ca (α, P ) reaction. It seems that the WS ( squared Woods-Saxon ) , WS^2.65 and WS⁵ potential can not provide a correct description of the behaviour of the incident α channel wave functions, but with the L-dependent potential a reasonable result can be obtained.

We derive a unified multi-harmonic modulation solution of the incommensurate phase with a simple model by a method like that used in solving pendulum problems in mechanics. This solution reduces to single-harmonic modulation at the upper end of temperatures, and transforms into kink solution at the lower end of temperatures, The basic wave-vector decreases monotonically with temperature, as was observed in experimentation.

An extended ratio method is applied to some lattice models. We find the following interesting features: the extended method often appears to be smoother and better; the odd-even oscillations are reduced greatly; and the Neville tables often provide sequences with faster convergence rate.

The energy dispersive relation of surface dangling bond state on InP (ī ī ī) clear, surface has been measured bg the angle resolved photo-mission. The theoretical calculation based on a slab model and extended Hückel theory agreed well with the experimental result if a surface relaxed atomic structure model for InP (ī ī ī) (1x1) is postulated.

We report high transition temperature superconductivity in one unit-cell (UC) thick FeSe films grown on a Se-etched SrTiO₃(001) substrate by molecular beam epitaxy (MBE). A superconducting gap as large as 20 meV and the magnetic field induced vortex state revealed by in situ scanning tunneling microscopy (STM) suggest that the superconductivity of the 1 UC FeSe films could occur around 77 K. The control transport measurement shows that the onset superconductivity temperature is well above 50 K. Our work not only demonstrates a powerful way for finding new superconductors and for raising T_C, but also provides a well-defined platform for systematic studies of the mechanism of unconventional superconductivity by using different superconducting materials and substrates.

An intrinsic magnetic topological insulator (TI) is a stoichiometric magnetic compound possessing both inherent magnetic order and topological electronic states. Such a material can provide a shortcut to various novel topological quantum effects but remained elusive experimentally for a long time. Here we report the experimental realization of thin films of an intrinsic magnetic TI, MnBi$_{2}$Te$_{4}$, by alternate growth of a Bi$_{2}$Te$_{3}$ quintuple layer and a MnTe bilayer with molecular beam epitaxy. The material shows the archetypical Dirac surface states in angle-resolved photoemission spectroscopy and is demonstrated to be an antiferromagnetic topological insulator with ferromagnetic surfaces by magnetic and transport measurements as well as first-principles calculations. The unique magnetic and topological electronic structures and their interplays enable the material to embody rich quantum phases such as quantum anomalous Hall insulators and axion insulators at higher temperature and in a well-controlled way.

Based on dislocation theory, we investigate the mechanism of strain rate effect. Strain rate effect and dislocation motion are bridged by Orowan's relationship, and the stress dependence of dislocation velocity is considered as the dynamics relationship of dislocation motion. The mechanism of strain rate effect is then investigated qualitatively by using these two relationships although the kinematics relationship of dislocation motion is absent due to complicated styles of dislocation motion. The process of strain rate effect is interpreted and some details of strain rate effect are adequately discussed. The present analyses agree with the existing experimental results. Based on the analyses, we propose that strain rate criteria rather than stress criteria should be satisfied when a metal is fully yielded at a given strain rate.

Using the extremely sharp peak of backward cross section for polarized γ+e → H+e processes one could hopefully detect Higgs bosons in W-S model.

The periodic and chaotic behaviors for both long and short delay time are demonstrated successfully using a hybrid OBD. The degree of stability S is introduced into the dynamic equations of optical bistability with a delayed feedback. The instability threshold is S=2 for long delay time and S=l+π/2Q for short delay time.

By measuring the temperature of the crystallization front of salol by means of in situ observations on a thermally regulating stage, we have obtained the linear form of (T_S/L-T_M.B),i.e., the difference between the temperatures of the front and the melt block vs v, the solidified volume of the interface per second.

A formula of the critical temperature for superconductors with small λ is derived from the Eliashberg equation.

A comparison between the electron captures of ¹⁵⁸Tb and ¹⁵⁷Tb is presented. The practical merit of using ¹⁵⁷Tb electron capture rates as a tool for electron-neutrino mass determination is analysed and emphasized.

We attempt to discover some exact analytical models of the spherically symmetric spacetime of collapsing fluid under shearfree conditions. Two types of solution are considered: one is to impose a condition on the mass function, while the other is to restrict the pressure. We obtain five exact models in total, and some of them satisfy the Darmois conditions.

Initial flow stress in tension and tension plus compression and coercivity after those processes in dual-phase steels have been measured. It was found that the values of coercivity for tension plus compression are smaller than for pure tension, a phenomenon much like the Bauschinger effect in steels.

We investigate the detailed epidemic spreading process in scale-free networks with link weights that denote familiarity between two individuals. It is found that the spreading velocity reaches a peak quickly then decays in a power-law form. Numerical study exhibits that the nodes with larger strength is preferential to be infected, but the hierarchical dynamics are not clearly found, which is different from the well-known result in the unweighed network case. In addition, also by numerical study, we demonstrate that larger dispersion of weight of networks results in slower spreading, which indicates that epidemic spreads more quickly on unweighted scale-free networks than on weighted scale-free networks with the same condition.

The modified simple equation method is employed to construct the exact solutions involving parameters of nonlinear evolution equations via the (1+1)-dimensional modified KdV equation, and the (1+1)-dimensional reaction-diffusion equation. When these parameters are taken to be special values, the solitary wave solutions are derived from the exact solutions. It is shown that the proposed method provides a more powerful mathematical tool for solving nonlinear evolution equations in mathematical physics.

We report a new kagome quantum spin liquid candidate Cu$_3$Zn(OH)$_6$FBr, which does not experience any phase transition down to 50 mK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature ($\sim$200 K). A clear gap opening at low temperature is observed in the uniform spin susceptibility obtained from $^{19}$F nuclear magnetic resonance measurements. We observe the characteristic magnetic field dependence of the gap as expected for fractionalized spin-1/2 spinon excitations. Our experimental results provide firm evidence for spin fractionalization in a topologically ordered spin system, resembling charge fractionalization in the fractional quantum Hall state.

High resolution angle-resolved photoemission measurements have been carried out to study the superconducting gap in the (Ba_0.6K_0.4)Fe₂As₂ superconductor with T_c=35 K. Two hole-like Fermi surface sheets around the Γ point exhibit different superconducting gaps. The inner Fermi surface sheet shows larger (10~12 meV) and slightly momentum-dependent gap while the outer one has smaller (7~8meV) and nearly isotropic gap. The lack of gap node in both Fermi surface sheets favours s-wave superconducting gap symmetry. Superconducting gap opening is also observed at the M(π,π) point. The two Fermi surface spots near the M point are gapped below T_c but the gap persists above T_c. The rich and detailed superconducting gap information will provide key insights and constraints in understanding pairing mechanism in the iron-based superconductors.

Undoped and copper doped zinc oxide (ZnO) thin films have been prepared on glass substrates by spray pyrolysis technique. The films were doped with copper using the direct method by addition of a copper salt (CuCl₂) in the spray solution of ZnO. Variation of structural, electrical, optical and thermoluminescence (TL) properties with doping concentrations is investigated in detail.

Using the adaptive time-dependent density-matrix renormalization group method, the dynamics of entanglement and quantum discord of an one-dimensional spin-1/2 XXZ chain is studied when anisotropic interaction quenches are applied at different temperatures. The dynamics of the quantum discord and pairwise entanglement between the nearest qubits shows that the entanglement and quantum discord will first oscillate and then approach to a constant value. The quantum discord can be used to predict the quantum phase transition, while the entanglement cannot.

Devices of electric double-layer transistors (EDLTs) with ionic liquid have been employed as an effective way to dope carriers over a wide range. However, the induced electronic states can hardly survive in the materials after releasing the gate voltage $V_{\rm G}$ at temperatures higher than the melting point of the selected ionic liquid. Here we show that a permanent superconductivity with transition temperature $T_{\rm c}$ of 24 and 15 K is realized in single crystals and polycrystalline samples of HfNCl and ZrNCl upon applying proper $V_{\rm G}$'s at different temperatures. Reversible change between insulating and superconducting states can be obtained by applying positive and negative $V_{\rm G}$ at low temperature such as 220 K, whereas $V_{\rm G}$'s applied at 250 K induce the irreversible superconducting transition. The upper critical field $H_{\rm c2}$ of the superconducting states obtained at different gating temperatures shows similar temperature dependence. We propose a reasonable scenario that partial vacancy of Cl ions could be caused by applying proper $V_{\rm G}$'s at slightly higher processing temperatures, which consequently results in a permanent electron doping in the system. Such a technique shows great potential to systematically tune the bulk electronic state in the similar two-dimensional systems.

The organic-inorganic hybrid perovskite CH$_{3}$NH$_{3}$PbI$_{3}$ has attracted significant interest for its high performance in converting solar light into electrical power with an efficiency exceeding 20%. Unfortunately, chemical stability is one major challenge in the development of CH$_{3}$NH$_{3}$PbI$_{3}$ solar cells. It was commonly assumed that moisture or oxygen in the environment causes the poor stability of hybrid halide perovskites, however, here we show from the first-principles calculations that the room-temperature tetragonal phase of CH$_{3}$NH$_{3}$PbI$_{3}$ is thermodynamically unstable with respect to the phase separation into CH$_{3}$NH$_{3}$I + PbI$_{2}$, i.e., the disproportionation is exothermic, independent of the humidity or oxygen in the atmosphere. When the structure is distorted to the low-temperature orthorhombic phase, the energetic cost of separation increases, but remains small. Contributions from vibrational and configurational entropy at room temperature have been considered, but the instability of CH$_{3}$NH$_{3}$PbI$_{3}$ is unchanged. When I is replaced by Br or Cl, Pb by Sn, or the organic cation CH$_{3}$NH$_{3}$ by inorganic Cs, the perovskites become more stable and do not phase-separate spontaneously. Our study highlights that the poor chemical stability is intrinsic to CH$_{3}$NH$_{3}$PbI$_{3}$ and suggests that element-substitution may solve the chemical stability problem in hybrid halide perovskite solar cells.

Symmetry plays fundamental role in physics and the nature of symmetry changes in non-Hermitian physics. Here the symmetry-protected scattering in non-Hermitian linear systems is investigated by employing the discrete symmetries that classify the random matrices. The even-parity symmetries impose strict constraints on the scattering coefficients: the time-reversal ($C$ and $K$) symmetries protect the symmetric transmission or reflection; the pseudo-Hermiticity ($Q$ symmetry) or the inversion ($P$) symmetry protects the symmetric transmission and reflection. For the inversion-combined time-reversal symmetries, the symmetric features on the transmission and reflection interchange. The odd-parity symmetries including the particle-hole symmetry, chiral symmetry, and sublattice symmetry cannot ensure the scattering to be symmetric. These guiding principles are valid for both Hermitian and non-Hermitian linear systems. Our findings provide fundamental insights into symmetry and scattering ranging from condensed matter physics to quantum physics and optics.

The differential cross sections of ¹⁷F and ¹⁷O elastic scattering products on ²⁰⁸Pb have been measured at the Radioactive Ion Beam Line at Lanzhou (RIBLL). Two angular dispersion plots of ln(dσ/dθ) versus θ² are obtained from the angular distribution of the elastic scattering differential cross sections. The angular dispersion plot exhibits a clear turning point for ¹⁷F in the range of small scattering angles 6--20° due to its exotic structure, but for ¹⁷O, the turning point is not observed in the same angular range. The experimental results have been compared with previous data of other groups. Systematical analysis on the available data supports the above conclusion that there is an exotic behaviour of the angular dispersion plot of weakly bound nuclei with halo or skin structure as compared with that of the ordinary nuclei near stable line. Therefore the turning point of the angular dispersion plot appears at small angle for weakly bound nuclei with halo or skin structure, and can be used as a new probe to investigate the halo and skin phenomena of weakly bound nuclei.