We study the Alice–Bob peakon system generated from an integrable peakon system using the strategy of the so-called Alice–Bob non-local KdV approach [Scientific Reports 7 (2017) 869]. Nonlocal integrable peakon equations are obtained and shown to have peakon solutions.

We study optical localized waves on a plane-wave background in negative-index materials governed by the defocusing nonlinear Schrödinger equation with self-steepening effect. Important characteristics of localized waves, such as the excitations, transitions, propagation stability, and mechanism, are revealed in detail. An intriguing sequential transition that involves the rogue wave, antidark–dark soliton pair, antidark soliton and antidark soliton pair can be triggered as the self-steepening effect attenuates. The corresponding phase diagram is established in the defocusing regime of negative-index materials. The propagation stability of the localized waves is confirmed numerically. In particular, our results illuminate the transition mechanism by establishing the exact correspondence between the transition and the modulation instability analysis.

A differential accelerometer comprising of two rotating masses made of the same material is proposed for drop tower-based free-fall testing of the spin–spin force between the rotating mass and the Earth. The measurement is performed by placing the two concentric masses of very different momenta in a vacuum drop capsule which is falling freely in the Earth's gravitational field. A nonzero output of the differential accelerometer is an indication of possible violation of new equivalence principle (NEP). We present the conceptual design of a modified free-fall NEP experiment which can be performed at the Beijing drop tower. Design and evaluation of the differential accelerometer with a hybrid electrostatic/magnetic suspension system are presented to accommodate for operation on ground and drop-tower tests. Details specific to the measurement uncertainty are discussed to yield an NEP test accuracy of $7.2\times10^{-9}$.

The strong force effect on gluon distribution of quark-gluon plasma and its influence on jet energy loss with detailed balance are studied. We solve the possibility equation and obtain the value of non-extensive parameter $q$. In the presence of strong interaction, more gluons stay at low-energy state than the free gluon case. The strong interaction effect is found to be important for jet energy loss with detailed balance at intermediate jet energy. The energy gain via absorption increases with the strong interaction. This will affect the nuclear modification factor $R_{\rm AA}$ and the parameter of $\hat{q}$ at intermediate jet energy.

The total and partial charge-changing cross sections of $^{28}$Si on carbon targets at 736 and 723 A MeV are studied by CR-39 plastic nuclear track detectors using the HSP-1000 microscope system and the PitFit track measurement software. The values of the total charge-changing cross section are $\sigma_{\rm tot}=(1179\pm50)$ mb and $\sigma_{\rm tot}=(1186\pm42)$ mb at 736 and 723 A MeV, respectively. The result is compared with the ones obtained by other experimental and theoretical results. The odd–even effect of the partial charge-changing cross section is observed.

We measure the rotational populations of ultracold $^{85}$Rb$^{133}$Cs molecules in the lowest vibrational ground state by a depletion spectroscopy and quantify the molecular production rate based on the measurement of single ion signal area. The $^{85}$Rb$^{133}$Cs molecules in the $X^{1}{\it \Sigma}^{+} (v=0)$ are formed from the short-range $(2)^{3}{\it \Pi}_{0^{+}}(v=10,J=0)$ molecular state. A home-made external-cavity diode laser is used as the depletion laser to measure the rotational populations of the formed molecules. Based on the determination of single ion signal, the production rates of molecules in the $J=0$ and $J=2$ rotational levels are derived to be 4800 mole/s and 7200 mole/s, respectively. The resolution and quantification of molecules in rotational states are facilitative for the manipulation of rotational quantum state of ultracold molecules.

Zeeman effect at the hyperfine level of the rovibronic ground state of I$^{35}$Cl are determined on the basis of $|I_{1}JF_{1}I_{2}FM_{F}\rangle$ via an effective Hamiltonian matrix diagonalization method. Perturbations of the Zeeman sublevels are observed and the perturbation selection rules are summarized as well. Several potential applications of such Zeeman effect are suggested.

FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)

We present an all-optical nonreturn-to-zero/return-to-zero (NRZ/RZ) to carrier-suppressed return-to-zero (CSRZ) format conversion scheme for differential phase-shift keying (DPSK) signals. The conversion is based on nonlinear polarization rotation of a semiconductor optical amplifier (SOA). The 4-channel NRZ-DPSK or RZ-DPSK signals at 10 Gb/s are simultaneously converted to the corresponding CSRZ-DPSK signals, with $-$0.8 and 1.4 dB average power penalties, respectively. Additionally, high quality format conversion performances are shown with the optical spectra and eye diagrams.

An $8\times10$ GHz receiver optical sub-assembly (ROSA) consisting of an 8-channel arrayed waveguide grating (AWG) and an 8-channel PIN photodetector (PD) array is designed and fabricated based on silica hybrid integration technology. Multimode output waveguides in the silica AWG with 2% refractive index difference are used to obtain flat-top spectra. The output waveguide facet is polished to 45$^{\circ}$ bevel to change the light propagation direction into the mesa-type PIN PD, which simplifies the packaging process. The experimental results show that the single channel 1 dB bandwidth of AWG ranges from 2.12 nm to 3.06 nm, the ROSA responsivity ranges from 0.097 A/W to 0.158 A/W, and the 3 dB bandwidth is up to 11 GHz. It is promising to be applied in the eight-lane WDM transmission system in data center interconnection.

Spectral imaging is an important tool for a wide variety of applications. We present a technique for spectral imaging using computational imaging pattern based on compressive sensing (CS). The spectral and spatial information is simultaneously obtained using a fiber spectrometer and the spatial light modulation without mechanical scanning. The method allows high-speed, stable, and sub sampling acquisition of spectral data from specimens. The relationship between sampling rate and image quality is discussed and two CS algorithms are compared.

A femtosecond optical Kerr gate time-gated ballistic imaging method is demonstrated to image a transparent object in a turbid medium. The shape features of the object are obtained by time-resolved selection of the ballistic photons with different optical path lengths, the thickness distribution of the object is mapped, and the maximum is less than 3.6%. This time-resolved ballistic imaging has potential applications in studying properties of the liquid core in the near field of the fuel spray.

Thermal convection in a three-dimensional tilted rectangular cell with aspect ratio 0.5 is studied using direct numerical simulations within both Oberbeck–Boussinesq (OB) approximation and strong non-Oberbeck–Boussinesq (NOB) effects. The considered Rayleigh numbers $Ra$ range from $10^5$ to $10^7$, the working fluid is air at 300 K, and the corresponding Prandtl number $Pr$ is 0.71. Within the OB approximation, it is found that there exist multiple states for $Ra=10^5$ and hysteresis for $Ra=10^6$. For a relatively small tilt angle $\beta$, the large-scale circulation can either orient along one of the vertical diagonal planes (denoted by $M_{\rm d}$ mode) or orient parallel to the front wall (denoted by $M_{\rm p}$ mode). Which of the two modes transports heat more efficiently is not definitive, and it depends on the Rayleigh number $Ra$. For $Ra=10^7$ and $\beta=0^\circ$, the time-averaged flow field contains four rolls in the upper half and lower half of the cell, respectively, $M_{\rm d}$ and $M_{\rm p}$ modes only developing in tilted cells. By investigating NOB effects in tilted convection for fixed $Ra=10^6$, it is found that the NOB effects on the Nusselt number $Nu$, the Reynolds number $Re$ and the central temperature $T_{\rm c}$ for different $\beta$ ranges are different. NOB effects can either increase or decrease $Nu$, $Re$ and $T_{\rm c}$ when $\beta$ is varied.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

Silica-coated carbonyl iron particles (CIPs) are fabricated with the Stober method to improve their heat-resistance and wave-absorption properties. The morphology, heat-resistance, electromagnetic properties and microwave absorption of raw-CIPs and silica-coated CIPs are investigated using a scanning electron microscope, an energy dispersive spectrometer, a thermal-gravimetric analyzer, and a network analyzer. The results show that the heat-resistance of silica-coated CIPs is better than that of raw CIPs. The reflection losses exceeding $-$10 dB of silica-coated CIPs are obtained in the frequency range 9.3–12.4 GHz for the absorber thickness of 2.3 mm, and the same reflection losses of uncoated CIPs reach the data in the lower frequency range for the same thickness. The enhanced microwave absorption of silica-coated CIPs can be ascribed to the combination of proper electromagnetic impedance match and the decrease of dielectric permittivity.

CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES

We study the strength and texture of tantalum (Ta) under uniaxial compression up to 80 GPa using an angle-dispersive radial x-ray diffraction technique together with the lattice strain theory in a diamond anvil cell at ambient temperature. The ratio of differential stress to shear modulus ($t/G$) is found to remain constant above $\sim$60 GPa, indicating that the Ta starts to experience macro yield with plastic deformation at this pressure. Combined with independent constraints on the high-pressure shear modulus, we find that the Ta sample could support a differential stress of $\sim$4.67 GPa when it starts to yield with plastic deformation at $\sim$60 GPa under uniaxial compression. The differential stress in Ta ranges from 0.216 GPa to 4.67 GPa with pressure increasing from 1 GPa to 60 GPa and can be expressed as $t=0.199(33)+0.075(1)P$, where $P$ is the pressure in GPa. A maximum differential stress as high as $\sim$5.37 GPa can be supported by Ta at the high pressure of $\sim$80 GPa. In addition, we investigate the texture of Ta under nonhydrostatic compression to 80 GPa using the software package material analysis using diffraction. It is proven that the plastic deformation due to stress under high pressures is responsible for the development of texture.

Development of graphene field effect transistors (GFETs) faces a serious challenge of graphene interface to the dielectric material. A single layer of intrinsic graphene has an average sheet resistance of the order of 1–5 k$\Omega/\square$. The intrinsic nature of graphene leads to higher contact resistance yielding into the outstanding properties of the material. We design a graphene matrix with minimized sheet resistance of 0.185 $\Omega/\square$ with Ag contacts. The developed matrices on silicon substrates provide a variety of transistor design options for subsequent fabrication. The graphene layer is developed over 400 nm nickel in such a way as to analyze hypersensitive electrical properties of the interface for exfoliation. This work identifies potential of the design in the applicability of few-layer GFETs with less process steps with the help of analyzing the effect of metal contact and post-process annealing on its electrical fabrication.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

La$_{2}$VMnO$_{6}$ is measured to be insulating and ferrimagnetic experimentally. In this study, by substituting V with Nb, La$_{2}$NbMnO$_{6}$ is investigated using the density functional theory. The calculated results indicate that La$_{2}$NbMnO$_{6}$ is also ferrimagnetic and exhibits the half metallic properties due to the strong electron correlation of Mn. The valence states of Nb and Mn are assigned to be +4 and +2 in La$_{2}$NbMnO$_{6}$, respectively, which are different from V$^{3+}$/Mn$^{3+}$ in La$_{2}$VMnO$_{6}$.

Using first-principles density functional theory combined with nonequilibrium Green's function method, we investigate the spin caloritronic transport properties of (2$\times$1) reconstructed zigzag MoS$_{2}$ nanoribbons. These systems can exhibit obvious spin Seebeck effect. Furthermore, by tuning the external magnetic field, a thermal giant magnetoresistance up to 10$^{4}$% can be achieved. These spin caloritronic transport properties are understood in terms of spin-resolved transmission spectra, band structures, and the symmetry analyses of energy bands around the Fermi level.

We report the growth process of FeTe$_{1-x}$Se$_x$ ($0\le x \le 1$) monolayer films on SrTiO$_{3}$ (STO) substrates through molecular beam epitaxy and discuss the possible ways to improve the film quality. By exploring the parameters of substrate treatment, growth control and post growth annealing, we successfully obtain a series of FeTe$_{1-x}$Se$_x$ monolayer films. In the whole growth process, we find the significance of the temperature control through surface roughness monitored by the reflection high-energy electron diffraction and scanning tunneling microscopy. We obtain the best quality of FeSe monolayer films with the STO substrate treated at $T=900$–$950^{\circ\!}$C before growth, the FeSe deposited at $T=310^{\circ\!}$C during growth and annealed at $T=380^{\circ\!}$C after growth. For FeTe$_{1-x}$Se$_x$ ($x < 1$), both the growth temperature and annealing temperature decrease to $T=260^{\circ\!}$C. According to the angle-resolved photoemission spectroscopy measurements, the superconductivity of the FeTe$_{1-x}$Se$_x$ film is robust and insensitive to Se concentration. All the above are instructive for further investigations of the superconductivity in FeTe$_{1-x}$Se$_x$ films.

A tunable absorber, composed of a graphene ribbon on two layers of TiO$_{2}$-Au between two slabs of dielectric material all on a metal substrate, is designed and numerically investigated. The absorption of the composite structure varies with the geometrical parameters of the structure and the physical parameters of graphene at mid-infrared frequencies. The numerical simulation shows that a near-perfect absorption with single and dual bands can be achieved in a certain frequency range. We also analyze the electric and surface current distributions to study the dual-band absorber. The results show that the absorber can be tuned by the chemical potential and electron–phonon relaxation time of graphene, and electromagnetically induced transparency phenomenon can be obtained. The results of this study may be beneficial in the fields of infrared communication, perfect absorbers, sensors and filters.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

We investigate the strain in various Ge-on-insulator (GeOI) micro-structures induced by three phase-change materials (PCMs) (Ge$_{2}$Sb$_{2}$Te$_{5}$, Sb$_{2}$Te$_{3}$, GeTe) deposited. The PCMs could change the phase from amorphous state to polycrystalline state with a low temperature thermal annealing, resulting in an intrinsic contraction in the PCM films. Raman spectroscopy analysis is performed to compare the strain induced in the GeOI micro-structures by various PCMs. By comparison, Sb$_{2}$Te$_{3}$ could induce the largest amount of tensile strain in the GeOI micro-structures after the low temperature annealing. Based on the strain calculated from the Raman peak shifts, finite element numerical simulation is performed to calculate the strain-induced electron mobility enhancement for Ge n-MOSFETs with PCM liner stressors. With the adoption of Sb$_{2}$Te$_{3}$ liner stressor, 22% electron mobility enhancement at $N_{\rm inv}=1\times10^{13}$ cm$^{-2}$ could be achieved, suggesting that PCM especially Sb$_{2}$Te$_{3}$ liner stressor is a promising technique for the performance enhancement of Ge MOSFETs.

The radiation shielding characteristics of 50 wt% WO$_{3}$/E44 epoxy composite in various gamma energies from 80 keV to 1.33 MeV are investigated via the MCNP code. Thus two scales are considered for WO$_{3}$ filler particles: micro and nano with sizes of 1 μm and 50 nm, respectively. The simulation results show that WO$_{3}$ nano particles exhibit a larger increase in linear attenuation coefficient in comparison with micro size particles. Finally, validation of simulation results with the published experimental data shows a good agreement.

The $\delta$-AlOOH can transport water into the deep mantle along cold subducting slab geotherm. We investigate the hydrogen-bond symmetrization behavior of $\delta$-AlOOH under the relevant pressure-temperature condition of the lower mantle using ab initio molecular dynamics (MD). The static symmetrization pressure of 30.0 GPa can be reduced to 17.0 GPa at 300 K by finite-temperature ($T$) statistics, closer to the experimental observation of $\sim $10.0 GPa. The symmetrization pressure obtained by MD simulation is related to $T$ by $P\,({\rm GPa})=13.9\,({\rm GPa})+0.01\,({\rm GPa/K})\times T\,({\rm K})$. We conclude that $\delta$-AlOOH in the lower mantle exists with symmetric hydrogen bond from its birthplace, or someplace slightly deeper, to the core-mantle boundary (CMB) along cold subducting slab geotherm. The bulk modulus decreases with $T$ and increases anomalously upon symmetrization: $K_{0}\,({\rm GPa})=181\,({\rm GPa})-0.013\,({\rm GPa/K})\times T\,({\rm K})$ for $\delta$-AlOOH with asymmetric hydrogen bond, and $K_{0}\,({\rm GPa})=216\,({\rm GPa})-0.013\,({\rm GPa/K})\times T\,({\rm K})$ for $\delta$-AlOOH with symmetric hydrogen bond. Our results provide an important insight into the existent form and properties of $\delta$-AlOOH in the lower mantle.

Silicon-germanium (SiGe) hetero-junction bipolar transistor current transients induced by pulse laser and heavy iron are measured using a real-time digital oscilloscope. These transients induced by pulse laser and heavy iron exhibit the same waveform and charge collection time except for the amplitude of peak current. Different laser energies and voltage biases under heavy ion irradiation also have impact on current transient, whereas the waveform remains unchanged. The position-correlated current transients suggest that the nature of the current transient is controlled by the behavior of the C/S junction.