[en] We investigate the formation of a heteronuclear tetramer A₃B by an Efimov-resonance-assisted stimulated Raman adiabatic passage scheme, which is considered a viable means of creating the homonuclear tetramer A₄[H. Jing and Y. Jiang, Phys. Rev. A 77, 065601 (2008)]. The atom-molecule dark-state solution for the system is derived, and the adiabatic conversion from atoms to heteronuclear tetramers is studied via the concept of adiabatic fidelity. In addition, the effects of external field parameters (including Rabi pulse strength, width, and single photon detuning) on the conversion are discussed.

[en] A first-principles investigation on the rupture strength W ₀ of γ-Ni/γ'-Ni₃Al interfaces with and without P-doping is conducted, and the influence of phosphorous content x on W ₀ is also evaluated. The results show P prefers to occupy Ni sublattices at the side of γ-phases rather than octahedral interstitial centers in γ and γ' phases. The advantages and adverse effects of phosphorous mainly depend on their inter-phase fracture sites related to doping types. With the increase of P content x, the Griffith rupture work W of Ni/Ni₃Al interfaces firstly decreases and then increases, and a minimum appears at x=0.018 wt.%. This good agreement with the x dependence of ultimate tensile strengths of IN718 superalloys indicates the W ₀ can be applied to characterize the tensile strength of Ni-based superalloys to some extent. The analysis of electronic structures reveal the detrimental effect of P-doping mainly originates from the weakened electronic affinity between interfacial atoms, but an elevated local elastic strain energy caused by substitution of P for Ni cannot be neglected. As a result, the P-doping at octahedral interstices in γ'-phases has a higher W than the substitution of P for Ni in γ-phases. (paper)

[en] The formation of mono-atomic tantalum (Ta) metallic glass (MG) through ultrafast liquid cooling is investigated by ab-initio molecular dynamics (MD) simulations. It is found that there exists nearly golden ratio order (NGRO) between the nearest and second nearest atoms in Ta MG, which has been indirectly confirmed by Khmich et al. and Liang et al.. The NGRO is another universal structural feature in metallic glass besides the local five-fold symmetry (LFFS). Further analyzing of electronic structure shows that the obvious orientation of covalent bond could be attributed to the NGRO in amorphous Ta at 300 K. (paper)

[en] Using a first-principles calculation, correlation between the chemical order and nature property of Cu-centered Cu_nZr_13-n(n = 6, 7, 8, 9) icosahedral clusters is investigated. It is found that homogeneous atoms in shell of Cu-Zr icosahedral clusters with low binding energy and high chemical stability prefer to bond each other. In this case, the Cu-Cu interaction is demonstrated to play a key role in the formation of stable Cu-centered Cu-Zr icosahedral clusters. Compared with other metastable Cu-centered Cu-Zr icosahedrons, both of ionic bonding between core and shell Cu atoms and covalent bonding between shell and shell Cu atoms in high stable icosahedrons are strong. An analysis of electronic structures has revealed that this atomic segregation in low energy and high chemical hardness of stable Cu-Zr icosahedral configurations can be attributed to themselves low N(E _F) at Femi level E _F to some extent. A further analysis of Mulliken’s population shows these shell Cu atoms are all donees in the formation of Cu-Zr icosahedral cluster, different from the donation of core Cu atoms and shell Zr atoms, and this charge transfer direction does not change with chemical order parameter δ _CuZr and chemical composition of Cu-centered Cu-Zr icosahedral clusters. (paper)

[en] The collective excitations of low-dimensional Bose-Einstein condensates with two- and three-body interactions in anharmonic potentials are investigated. Using the standard variational approach, the governing equations of motions for the low-energy excitations are obtained by solving time-dependent Gross-Pitaevskii-Ginzburg equation, and the excitation spectrums are calculated in small amplitude limit. The frequency shift and nonlinear mode coupling induced by the anharmonic distortion (adding cubic, quartic, or quintic term to a harmonic trap) are studied

[en] The identification and characterization of critical nuclei is a long-standing issue in the rapid solidification of metals and alloys. An ambiguous description for their sizes and shapes used to lead to an overestimation or underestimation of homogeneous nucleation rates $I\left(T\right)$ in the framework of classical nucleation theory (CNT). In this paper, a unique method able to distinguish the critical nucleus from numerous embryos is put forward on the basis of configuration heredities of clusters during rapid solidifications. As this technique is applied to analyze the formation and evolution of various fcc-Al single crystal clusters in a large-scale molecular dynamics simulation system, it is found that the size n _c and geometrical configuration of critical nuclei as well as their liquid–solid interfacial structure can be determined directly. For the present deep super-cooled system with an undercooling of $T_{\mathrm{m}}=0.42T_{\mathrm{m}}^{\mathrm{c}\mathrm{a}\mathrm{l}}$, the average size of critical nuclei is demonstrated to be $\stackrel{¯<!--\; ??\; -->}{n_{\mathrm{c}}}\approx <!--\; ???\; -->26$, but most of which are non-spherical lamellae. Also, their liquid–solid interfaces are revealed to be not an fcc-liquid duplex-phase interface but an fcc/hcp-liquid multi-phase structure. These findings shed some lights on the CNT, and a good agreement with previous simulations and experiments in $I\left(T\right)$ indicates this technique can be used to explore the early-stage of nucleation from atomistic levels. (paper)

[en] We investigate the guided modes in monolayer graphene-based waveguides with asymmetric quantum well structure induced by unequal dc voltages. The dispersion relation for the guided modes is obtained analytically, the structures of the guided modes are discussed under three distinct cases. For the cases of the classical motion and the Klein tunneling, the asymmetric structure does not influence the mode structures dramatically compared with that in the symmetric waveguide. But for the mixing case of the former two, the mode structures and the motion characteristics for the electron and the hole exhibit different behaviors at same condition. The results may be helpful for the practical application of graphene-based quantum devices.

[en] The evolution of Bose-Einstein condensates (BECs) loaded into a periodic ring optical lattices (OL) trap is studied. By means of the variational method and direct numerical simulations of the Gross-Pitaevskii (GP) equation, the ground state properties and the vortex stabilities of the condensates for both repulsive and attractive cases are investigated. The results show that the bound states exist for determinate OL strength and interatomic interaction. However, the ground states of BECs undergo delocalizing-localizing transition for both attractive and repulsive cases as the strength of the OL or the interatomic interaction is decreased below the critical value. The ring OL can suppress the delocalizing transition efficiently

[en] Undoped and La-doped ZnS thin films are prepared by chemical bath deposition (CBD) process through the co-precipitation reaction of inorganic precursors zinc sulfate, thiosulfate ammonia and La₂O₃. Composition of the films is analyzed using an energy-dispersive x-ray spectroscopy (EDS). Absorption spectra and spectral transmittances of the films are measured using a double beam UV-VIS spectrophotometer (TU-1901). It is found that significant red shifts in absorption spectra and decrease in absorptivity are obtained with increasing lanthanum. Moreover, optical transmittance is increased as La is doped, with a transmittance of more than 80% for wavelength above 360 nm in La-doped ZnS thin films. Compared to pure ZnS, the band gap decreases and flat-band potential positively shifts to quasi-metal for the La-doped ZnS. These results indicate that La-doped ZnS thin films could be valuably adopted as transparent electrodes. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] We address the nonlinear dynamics of binary Bose-Einstein condensates with mutually symmetric spinor components trapped in an optical lattice. The interaction between the repulsive Lee–Huang–Yang nonlinearity and the intercomponent attraction as well as Bragg scattering of an optical lattice results in formation of multi-peaked quantum droplets. Even- and odd-symmetric droplets can bifurcate from Bloch modes of the corresponding periodic systems. Linear stability analysis corroborated by direct evolution simulations reveals that even-symmetric droplets with different norms and different number of peaks can evolve stably at the same chemical potential, i.e., multi-stable droplets are possible in the present scheme. Besides the droplets in the semi-infinite gap, the properties of droplets in the first finite bandgap are also discussed. Both even- and odd-symmetric droplets are stable in almost their whole existence domains. We reveal that optical lattice plays an important role for the stabilization of droplets, in sharp contrast to the nonlinear system without a lattice modulation. We, thus, furnish a paradigmatic example of multi-stable quantum droplets held in optical lattices.