Modern Physics Letters B

Over the last decade, negative index media have attracted much attention due to their potential applications, especially the possibility of constructing superlenses. However, achieving high-performance negative-index metamaterials at visible frequencies, where this kind of media could find many applications, still remains a challenge. In this article, we provide a brief overview of the main routes for the implementation of metamaterials with negative index in this band, with a special focus on the so-called fishnet metamaterial. We pay particular attention to a specific fishnet configuration that recently allowed for the experimental demonstration of a low-loss and polarization-insensitive negative-index band in the visible regime.

In this work, we study the Silver mean sequence based on substitution rules by means of a transfer-matrix approach. Using transfer-matrix method, we find a recurrence relation for the traces of general transfer-matrices which characterizes electronic properties of the quasicrystal in question. We also find an invariant of the trace-map.

The focus of this study is to experimentally investigate the effect of debonding stress, the interface between the fibers and the polymer matrix, on the damping properties of the short fiberglass reinforced polymer composites. In this study, short fiberglass reinforced polycarbonate composite materials were fabricated and characterized for their tensile properties by varying the fiberglass loading fraction. The debonding stress was evaluated by coupling the acoustic emission technique with the tensile testing. After the determination of the debonding stress was completed, dynamic cyclic testing was performed in order to investigate the effect of debonding on the damping properties of the polymer composites. It was experimentally observed in this study that the debonding can facilitate the stick-slip friction under cyclic loadings, which then gives rise to better damping performance in the fiberglass composites.

We present an approach for effectively converting atomic Bose–Einstein condensate (BEC) into molecular one. Atoms are converted into molecules through a series of intermediate vibrational states by using chainwise stimulated Raman adiabatic passage technique. We utilize a feasible pulse sequence to achieve higher conversion efficiency by solving the coupled mean-field equations. As an example, we investigate the formation of Rb₂ and calculate conversion efficiency to be 92.3%.

The effect of strain on the electronic properties of BC₃ sheet was studied by using first-principles density functional theory. It is found that the band gap of BC₃ sheet increases gradually when the applied tensile strain ranges from 0% to 12.5%. While the band gap decreases as the compressive strain is applied, especially resulting in the semiconductor-metal transition at some strain. Further analysis shows that the change of band gap mainly results from the variation of the energy of valence band maximum (VBM), which is related to the strength of the bonding state. The proposed mechanical control of the electronic properties will widen the application of BC₃ sheet in future nanotechnology.

In this work, using the single-band Hubbard model, we numerically study the magnetic ordering in zigzag graphene nanoribbons (ZGNRs). We calculate density of states and charge density distribution in the ZGNR, and show the nontrivial behavior of its electronic band structure in the presence of an external transverse electric field. Then, the robustness of such edge magnetic ordering and consequent half-metallicity is investigated for nanoribbons defected with single-atom vacancies. Our results show that the nontrivial magnetic properties of ZGNRs are robust to an acceptable percentage of single atom vacancies.

In this paper, the effective capacitance between the origin (0, 0, 0) and any other lattice site (l₁, l₂, l₃), in an infinite simple cubic (SC) network consisting of identical capacitors each of capacitance C, has been expressed rationally in terms of the known value g_o and π. The asymptotic behavior is also investigated, and some numerical values for the effective capacitance are presented.

First-principles calculations based on the density functional theory (DFT) within the generalized gradient approximation (GGA) have been used to study Sc-doped TiO₂, rutile and anatase, crystals. Local defect microstructure, electronic and electrical properties have been obtained and discussed in the present work. Large radius hole polaron state found here points out to the possibility of p-type electrical conductivity in Sc-doped titania.

By using the first-principles methods based on density function theory (DFT), the effects of boron(B)/phosphorus(P) pair co-doping on the electrical properties of zigzag single-walled carbon nanotubes (SWNTs) have been investigated. We calculated the formation energies and band structures of (6, 0) metallic and (8, 0) semiconducting SWNTs with different B/P co-doping sites and concentrations. The obtained formation energies suggest that the B/P co-doping configurations are energetically stable structures and the B and P tend to form a B–P bond. It shows that an energy gap is opened by B/P co-doping in (6, 0) metallic SWNTs and the metallic carbon nanotubes are converted into semiconductors. For the (8, 0) semiconducting SWNTs, B/P co-doping influences the band structure, but it does not change the attributes essentially and the SWNTs are still semiconducting. It was also found that the band structures depend on the doping concentration as well as the doping site of B/P pair.

In this paper, we report on the influence of a square (triangular) trench on the superconducting properties of a perforated mesoscopic sample. Effects associated to the pinning force of the hole versus the pinning by the trench and interplay between the shape of the outer boundary and the shape of the inner defects on the vortex configuration are studied for a thin disk. Using the Ginzburg–Landau theory, we calculate the magnetization, vorticity, free energy, magnetic induction, supercurrent and superconducting order parameter as a function of the applied perpendicular magnetic field. We show that only in a restricted range of the magnetic field the vortex configuration obeys the geometry of the trench. Nevertheless, we clearly demonstrate that in our sample new phenomena are possible due to competing interactions of the geometry of the sample and the added geometry of the nanoengineered trench.