Modern Physics Letters B

The electronic structure of sodium tungsten bronzes Na_xWO₃ is investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES). The ARPES spectra measured in both insulating and metallic phases of Na_xWO₃ reveals the origin of metal-insulator transition (MIT) in sodium tungsten bronze system. It is found that in insulating Na_xWO₃ the states near the Fermi level (E_F) are localized due to the strong disorder caused by the random distribution of Na⁺ ions in WO₃ lattice. Due to the presence of disorder and long-range Coulomb interaction of conduction electrons, a soft Coulomb gap arises, where the density of states vanishes exactly at E_F. In the metallic regime the states near E_F are populated and the Fermi level shifts upward rigidly with increasing electron doping (x). Volume of electron-like Fermi surface (FS) at the Γ(X) point of the Brillouin zone gradually increases with increasing Na concentration due to W 5d t_2g band filling. A rigid shift of the Fermi energy is found to give a qualitatively good description of the Fermi surface evolution. As we move from bulk-sensitive to more surface sensitive photon energy, we found the emergence of Fermi surfaces at X(M) and M(R) points similar to the one at the Γ(X) point in the metallic regime, suggesting that the reconstruction of surface was due to rotation/deformation of WO₆ octahedra.

By using of the invariant theory, we have studied the generalized time-dependent giant spin model. The dynamical and geometric phases are given, respectively. The Aharonov–Anandan phase is also obtained under the cyclical evolution.

We derive an analytic expression for the Goos–Hänchen shift experienced by an acoustic wave that is totally reflected at the interface between a negative-refractive-index acoustic medium and a positive-index acoustic medium. Upon obtaining the condition necessary for phonon-trapping in a three-layer heterostructure, we introduce a design for an "acoustic clepsydra" by using a suitable acoustic heterostructure.

On the condition of electron–LO-phonon strong coupling in an anisotropic qunntum dot (QD), the eigenenergies of the ground-state and the first excited state, the eigenfunctions of the ground-state and the first excited state are obtained by using a variational method of Pekar type. This system in QD may be employed as a quantum system-qubit. Numerical calculations are performed on the pure dephasing factor. The relations of the pure dephasing factor on the temperature, the Coulomb binding parameter, the electron–LO-phonon coupling strength and the effective confinement length are derived.

The generalized nonlinear Schrödinger equation with the variable coefficient is discussed, and the exact dark N-soliton solution is presented by using the Hirota bilinear method, from finding the 1-soliton to 2-soliton, and then we obtain the N-soliton solution. With the aid of Maple, a few figures of solutions under several different cases are shown when aleatoric constants and variables are given exact values.

The dynamic relaxation of the German DAX both before and after a large price-change is investigated. The dynamic behavior is characterized by a power law. At the minutely time scale, the exponent p governing the power-law behavior takes a same value before and after the large price change, while at the daily time scale, it is different. Numerical simulations of an interacting EZ herding model are performed for comparison.

Super-dispersive long wave hierarchy is obtained by use of the Lie super-algebra B(0, 1), then the super-Hamiltonian structure of the above system is given by the associated supertrace identity. The method can be used to produce the super-Hamiltonian structures of the other superintegrable systems.

A super-Burgers hierarchy and its super-Hamiltonian structure is obtained respectively based on Lie super-algebra and is associated with super-trace identity.

The co-doping effect of Zn and Pr impurities in the compounds of composition Y_1-xPr_xBa₂[Cu_1-yZn_y]₃O_7-δ with x = 0.1, x = 0.2 and 0 ≤ y ≤ 0.1 has been investigated by analyzing the results of electrical resistivity measurements. It is found that for Pr substitution at x = 0.1, there is a minimal influence on in-plane processes, thereby slightly affecting T_c and residual resistivity ρ₀, but with the resistivity slope dρ/dT becoming large for the range of y from 0.03 to 0.06, leading to a larger depinning effect. For x = 0.2 a drastic change is observed whereby ρ₀ becomes abnormally large, and dρ/dT becomes negative, implying totally pinned charge stripes and no depinning. This second observation therefore suggests that Pr substitution converts the overdoped system to an optimally doped system, leading to the universal superconductor–insulator transition.

A novel mixed organic single crystal of glycine thiourea (GTU), which is a potential material for nonlinear optical applications, has been grown by solvent evaporation method at room temperature. The grown single crystal has been analyzed using different characterization methods. X-ray diffraction studies show that it belongs to an orthorhombic crystal system having lattice dimensions a = 5.546 Å, b = 7.774 Å and c = 8.637 Å. The formation of the compound was verified by FTIR analysis. Its optical behavior was analyzed using UV-vis analysis and it was found that it had good optical transmission in the entire visible region. The mechanical properties of grown crystals were studied using Vickers microhardness tester. The surface defects were examined by adopting an etching technique. Its nonlinear optical property was tested using Kurtz powder method and found to have better SHG efficiency than that of potassium dihydrogen phosphate (KDP) single crystal.