We investigate the dynamics of coherence for a central two-qubit system coupled to an $XY$ spin chain with the Dzyaloshinsky–Moriya interaction. It is found that a sudden transition of coherence exists near the critical point in the weak-coupling case, and an oscillatory envelope appears in the strong-coupling case. In both cases the freezing phenomenon of coherence can be found.

The closure of a turbulence field is a longstanding fundamental problem, while most closure models are introduced in spectral space. Inspired by Chou's quasi-normal closure method in spectral space, we propose an analytical closure model for isotropic turbulence based on the extended scale similarity theory of the velocity structure function in physical space. The assumptions and certain approximations are justified with direct numerical simulation. The asymptotic scaling properties are reproduced by this new closure method, in comparison to the classical Batchelor model.

We demonstrate a triple-pass scheme for coherent transfer of optical frequency and the delay effect on the fiber phase noise compensation. It is theoretically proved that the delay effect consists of both fiber delay and servo delay. The delay effect confines the servo bandwidth within $1/8\tau$ and induces a residual fiber phase noise after noise compensation. For a 25-km-long fiber, the servo bandwidth is found to be around 1 kHz, and the fiber phase noise is suppressed approaching to the theoretical limitation. The triple-pass scheme enables the simultaneous transfer of optical frequency to multiple remote users. The performance of noise compensator in the triple-pass scheme can achieve a similar level result compared with that in the double-pass scheme.

A new $^{11}$Be($p$,$d$) transfer reaction experiment is performed in inverse kinematics with a radioactive $^{11}$Be beam at 26.9$A$ MeV. Three low-lying states, namely the 0$^{+}$ ground state, the 2$^{+}$ state at $E_x=3.37$ MeV, and the multiplet at around 6 MeV in $^{10}$Be, are populated by this one-neutron transfer reaction. These three states in $^{10}$Be are clearly discriminated from the $Q$-value spectrum, which is rebuilt from energies and angles of the recoil deuterons in coincidence with $^{10}$Be. A spectroscopic factor for each state is extracted by comparing the experimental differential cross sections to the theoretical calculation results using the finite range adiabatic distorted wave approximation method with different global nucleon-nucleus potentials. It is found that the newly extracted spectroscopic factors for the 0$^+$ and 2$^+$ states are consistent with the previous ones, but the factor for the multiplet is smaller than the value in the reference, and the possible reason is discussed.

Doping is an effective approach for improving the photovoltaic performance of Cu$_{2}$ZnSnS$_{4}$ (CZTS). The doping by substitution of Cu atoms in CZTS with Li and Ag atoms is investigated using density functional theory. The results show that the band gaps of Li$_{2x}$Cu$_{2(1-x)}$ZnSnS$_{4}$ and Ag$_{2x}$Cu$_{2(1-x)}$ZnSnS$_{4}$ can be tuned in the ranges of 1.30–3.43 and 1.30–1.63 eV, respectively. The calculation also reveals a phase transition from kesterite to wurtzite-kesterite for Li$_{2x}$Cu$_{2(1-x)}$ZnSnS$_{4}$ as $x$ is larger than 0.9. The tunable band gaps of Li$_{2x}$Cu$_{2(1-x)}$ZnSnS$_{4}$ and Ag$_{2x}$Cu$_{2(1-x)}$ZnSnS$_{4}$ make them beneficial for achieving band-gap-graded solar cells.

Nanofibers have many promising applications because of their advantages of high power density and ultralow saturated light intensity. We present here a Zeeman shift of the Doppler-broadened cesium D$_2$ transition using a tapered optical nanofiber in the presence of a magnetic field. When a weak magnetic field is parallel to the propagating light in the nanofiber, the Zeeman shift rates for different circularly polarized spectra are observed. For the $\sigma^{+}$ component, the typical linear Zeeman shift rates of $F=3$ and $F=4$ ground-state cesium atoms are measured to be 3.10($\pm$0.19) MHz/G and 3.91($\pm$0.16) MHz/G. For the $\sigma^{-}$ component, the values are measured to be $-$2.81($\pm$0.25) MHz/G, and $-$0.78($\pm$0.28) MHz/G. The Zeeman shift using the tapered nanofiber can help to develop magnetometers to measure the magnetic field at the narrow local region and the dispersive signal to lock laser frequency.

We propose a new method to separate different orders of an all-fiber passive Q-switching stimulated Brillouin scattering (SBS) laser. We use two fiber Bragg gratings connected by two circulators for the filtering. We obtain a stabilized pulse laser and measure the pulse width of different orders. The first order of SBS has a central wavelength of 1549.75 nm, an average output power of 9 mW, and a pulse width of 400 ns. The pulse width of SBS is reduced by the higher-order signals with the larger fluctuations.

An experimental scheme to simultaneously obtain the information of fringe visibility and path predictability is designed. In a modified Young's double-slit experiment, two density filters rotating at different frequencies are placed before the two pineholes to encode path information. The spatial and temporal distributions of the output provide us with the wave and particle information of the single photons, respectively. The simultaneous measurement of the wave and particle information inevitably disturbs the system and thus causes some loss of the duality information, which is equal to the mixedness of the photonic state behind the density filters.

We present an efficient three-dimensional coupled-mode model based on the Fourier synthesis technique. In principle, this model is a one-way model, and hence provides satisfactory accuracy for problems where the forward scattering dominates. At the same time, this model provides an efficiency gain of an order of magnitude or more over two-way coupled-mode models. This model can be applied to three-dimensional range-dependent problems with a slowly varying bathymetry or internal waves. A numerical example of the latter is demonstrated in this work. Comparisons of both accuracy and efficiency between the present model and a benchmark model are also provided.

Dynamics of a single cavitation bubble in sodium dodecyl sulfate (SDS) aqueous solutions is investigated experimentally and theoretically. The bubble pulsation is measured by a phase-locked integrated imaging technique, and the ambient radius is obtained by fitting the numerical calculation based on the Rayleigh–Plesset bubble dynamics model to the experimental data. The results show that, under the same driving condition, the ambient radius of the cavitation bubble decreases correspondingly with the increase of SDS concentration within the critical micelle concentration, while the compression ratio of the radius increases, which indicates that the addition of SDS decreases the internal molecular number of the cavitation bubble and increases the power capability of the cavitation bubble. In addition, bubble oscillation increases the concentration of the surfactant molecules on the bubble wall, so that the effect of SDS on a single cavitation bubble is reduced when the SDS concentration is greater than 0.8 mM.

We investigate the rotational dynamics of a low-density sphere on the free surface of a vertically vibrated granular material (VGM). The dynamical behavior of the sphere is influenced by the external energy input from an electromagnetic shaker which is proportional to $\varepsilon$, where $\varepsilon$ is equal to the ratio between the square of the dimensionless acceleration ${\it \Gamma}$ and the square of the vibration frequency $f$ of the container. Empirical results reveal that as the VGM transits from local-to-global convection, an increase in $\varepsilon$ generally corresponds to an increase in the magnitudes of the rotational $\omega_{\rm RS}$ and translational $v_{\rm CM}$ velocities of the sphere, an increase in the observed tilting angle $\theta_{\rm bed}$ of the VGM bed, and a decrease in the time $t_{\rm wall}$ it takes the sphere to roll down the tilted VGM bed and hit the container wall. During unstable convection, an increase in $\varepsilon$ results in a sharp decrease in the sphere's peak and mean $\omega_{\rm RS}$, and a slight increase in $t_{\rm wall}$. For the range of $\varepsilon$ values covered in this study, the sphere may execute persistent rotation, wobbling or jamming, depending on the vibration parameters and the resulting convective flow in the system.

We study the interaction of a uniform, cold and collisional plasma with a test charged particle moving off-axis at a constant speed down a cylindrical tube with a resistive thick metallic wall. Upon matching the electromagnetic field components at all interfaces, the induced monopole electromagnetic fields in the plasma are obtained in the frequency domain. An expression for the plasma electric resistance and reactance is derived and analyzed numerically for some representative parameters. Near the plasma resonant frequency, the plasma resistance evolves with frequency like a parallel RLC resonator with peak resistance at the plasma frequency $\omega_{\rm pe}$, while the plasma reactance can be capacitive or inductive in nature depending on the frequency under consideration.

Thermal expansion is a common phenomenon in both metals and alloys, which is important for metallic material applications in modern industry, especially in nuclear and aerospace industries. A lower thermal expansion coefficient may cause lower thermal stress and higher accuracy. A new Zr-based alloy is developed and presented. The XRD diffraction results demonstrate that only a close-packed hexagonal phase ($\alpha$ or $\alpha'$ phase) exists in the microstructure. The thermal expansion and mechanical properties are studied. According to the experimental results, the new Zr-based alloy presents a low thermal expansion coefficient and good mechanical properties. Also, its thermal expansion coefficient is stable through solution treatment.

We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blue-detuned laser beam with a waist of 20 μm at a wavelength of 767 nm. We probe the variation of the atomic temperature and width versus the radio frequency in the evaporative cooling. Both the behaviors are in good agreement with the calculation of the trapping potential dressed by the rf signal above the threshold temperature, while deviating from the calculation near the phase transition. To accurately obtain the atomic width, we use the plugged hole as the reference to optimize the optical imaging system by precisely minimizing the artificial structures due to the defocus effect.

We report the epitaxial growth of single-crystalline CdTe(100) thin films on GaAs(100) substrates using molecular beam epitaxy. By controlling the substrate pre-heated temperature with adjustable Te flux, three different reconstructed surfaces are realized, and their influence on the subsequent CdTe growth is investigated. More importantly, we find that both the presence of a thin native oxide layer and the formation of Ga-As-Te bonds at the interface enable the growth along the (100) orientation and help to reduce the threading dislocations and other defects. Our results provide new opportunities for compound semiconductor heterogeneous growth via interfacial engineering.

The exciton states of semiconducting carbon nanotubes are calculated by a tight-binding model supplemented by Coulomb interactions under the combined effect of uniaxial strain and magnetic field. It is found that the excitation energies and absorption spectra of zigzag tubes (11,0) and (10,0) show opposite trends with the strain under the action of the magnetic field. For the (11,0) tube, the excitation energy decreases with the increasing uniaxial strain, with a splitting appearing in the absorption spectra. For the (10,0) tube, the variation trend firstly increases and then decreases, with a reversal point appearing in the absorption spectra. More interesting, at the reversal point the intensity of optical absorption is the largest because of the degeneracy of the two bands nearest to the Fermi Level, which is expected to be observed in the future experiment. The similar variation trend is also exhibited in the binding energy for the two kinds of semiconducting tubes.

The nitrogen dimer as both a fundamental building unit in designing a new type of nitrides, and a material gene associated with high electrical and thermal conductivities is investigated by first principles calculations. The results indicate that the predicted SiN$_{4}$ is structurally stable and reasonably energy-favored with a striking feature in its band structure that exhibits free electron-like energy dispersions. It possesses a high electrical conductivity ($5.07\times10^{5}$ S/cm) and a high thermal conductivity (371 W/m$\cdot$K) comparable to copper. The validity is tested by isostructural AlN$_{4}$ and SiC$_{4}$. It is demonstrated that the nitrogen dimers can supply a high density of delocalized electrons in this new type of nitrides.

Current-voltage electrical characteristics of Er silicide/Si(001) nanocontacts are measured in situ in a scanning tunneling microscopy system. Introduced as a new technique to suppress surface leakage conduction on Si(001), a silver wetting layer is evaporated onto the substrate surface kept at room temperature with ErSi$_{2}$ nanoislands already existing. The effects of the silver layer on the current-voltage characteristics of nanocontacts are discussed. Our experimental results reveal that the silver layer at coverage of 0.4–0.7 monolayer can suppress effectively the current contribution from the surface conduction path. After the surface leakage path of nanocontacts is obstructed, the ideality factor and the Schottky barrier height are determined using the thermionic emission theory, about 2 and 0.5 eV, respectively. The approach adopted here could shed light on the intrinsic transport properties of metal-semiconductor nanocontacts.

InGaN-based green light-emitting diodes (LEDs) with different green quantum well numbers grown on Si (111) substrates by metal organic chemical vapor deposition are investigated. It is observed that V-shaped pits appear in the AFM images with the green quantum well number increasing from 5 to 9, and results in larger reverse-bias leakage current. Meanwhile, in the case of the sample with the number from 5 to 7 then to 9, the external quantum efficiency increases firstly, and then decreases. These phenomena may be related to the size of V-shaped pits in the active area and the distribution of electrons and holes in the active area caused by V-shaped pits. The optimal number of green quantum wells is determined to be 7.

Though the quantum spin Hall effect (QSHE) in two-dimensional (2D) crystals has been widely explored, the experimental realization of quantum transport properties is only limited to HgTe/CdTe or InAs/GaSb quantum wells. Here we employ a tight-binding model on the basis of $d_{z^{2}}$, $d_{xy}$, and $d_{x^{2}-y^{2}}$ orbitals to propose QSHE in the triangular lattice, which are driven by a crossing of electronic bands at the ${\it \Gamma}$ point. Remarkably, 2D oxidized Mxenes W$_{2}$M$_{2}$C$_{3}$ are ideal materials with nontrivial gap of 0.12 eV, facilitating room-temperature observations in experiments. We also find that the nontrivially topological properties of these materials are sensitive to the cooperative effect of the electron correlation and spin-orbit coupling. Due to the feasible exfoliation from its 3D MAX phase, our work paves a new direction towards realizing QSHE with low dissipation.

We report on the tunneling anisotropic magnetoresistance in antiferromagnetic perpendicular tunnel junction consisting of $L1_{0}$-MnGa/FeMn/AlO$_{x}$/Pt grown on GaAs (001) substrates by molecular-beam epitaxy. The temperature-dependent perpendicular exchange bias effect reveals an exchange coupling between ferromagnetic $L1_{0}$-MnGa and antiferromagnetic FeMn. The rotation of antiferromagnetic spins in FeMn can be driven by perpendicularly magnetized $L1_{0}$-MnGa due to the exchange-spring effect at the interface and leads to room-temperature tunneling anisotropic magnetoresistance ratio of 0.86%. We also find that the tunneling anisotropic magnetoresistance strongly depends on temperature and angle. These results have broadened the material selection range for high performance antiferromagnetic spintronic devices.

A poly vinyl alcohol (PVA) scaffold with aligned porous is strengthened by in-situ combining with TiO$_{2}$. The increased freezing rate can be used to further increase the strength of aligned porous materials. The strengthened porous PVA exhibits aligned interconnected porous structures and shows a significant enhancement in tensile testing and compression strength testing.

The synergism effect of total ionizing dose (TID) on a single event transient (SET) in a bipolar comparator is investigated. Experimental results show that the shapes of the SET are considerably influenced by the TID accumulated in low dose rates. The variation tendency of SET shapes can be accurately simulated by temperature switching irradiation. The mechanism of this synergism effect is also analyzed in brief via the operating schematic of a comparator. After the accumulation of 100 krad(Si), the lower tendency of negative SET can be attributed to the degeneration of $\beta$. The change tendency of a positive SET, either lower or higher, is dependent on the load condition that limits the output range of the comparator.