Modern Physics Letters B

The shifts in field-cooling hysteresis loops of antiferromagnetic nanoparticle systems have been widely observed in experiments. Here, numerical calculation is used to study the influence of the surface anisotropy and defects. It is found that surface defects alone are sufficient to yield the loop shifts (LS) at proper field angles. Neither the disordered nor the radial surface anisotropy is the indispensable ingredient to generate the LS. However, both of them play a role in enhancing the LS. The possible mechanisms are discussed.

The lattice structure, interface binding energy, density of states, charge density difference and Bader charges of Au (100)/CH₃NH₃PbI₃ (MAPbI₃) (100) interface were studied with the first-principles calculations. The lattice mismatch of the Au (100)/MAPbI₃ (100) interface is 3.48%. The interface binding energy is −0.124 J/m². There is a small amount of electronic states nearby the interface through analyzing the density of states of the interface. In addition, the atom orbital has hybridizations nearby the interface. Through analyzing charge density difference and Bader charges, it is found that there is obvious charge transfer at the interface.

We have performed the first-principles pseudopotential calculations to investigate the structural phase transition and electronic properties of SbI₃ considering several possible phases as a function of pressure from 0 GPa to 100 GPa. Our calculations show that this material undertakes a structural transformation from the R-3 phase to high-pressure $P{2}_1/c$ phase at about 6.5 GPa with a relative volume collapse of 4.3%. We also have investigated the elastic properties and energy band structure of SbI₃ under hydrostatic pressure. The calculation suggests that the R-3 phase is a semiconductor with an indirect band gap of about 2.16 eV at 0 Gpa. Under the influence of pressure, we have found that high-pressure $P{2}_1/c$ phase has transformed to metal at about 55 GPa.

Two novel aluminum nitride (which is bct-AlN at ambient pressure, and h-AlN at higher pressure) were predicted using first-principles calculations. The mechanical and phonon dispersion results indicate that bct-AlN is mechanically and dynamically stable at zero pressure, h-AlN phase can be stabilized by increasing pressure and it is mechanically and dynamically stable at 10 GPa. bct-AlN is more favorable than rs-AlN in thermodynamics at ambient pressure. Our calculated band gap of bct-AlN is 5.85 eV. It can be used as semiconductor device and optoelectronic device due to its inherent wide direct band gap. For bct-AlN, the shortest Al–N bond length is 1.8476 Å and its bond order index is 1.28, which shows that strong covalent bonds are formed between Al atoms and N atoms. Moreover, the anisotropy of Young’s modulus and optical properties can be noticed obviously for bct-AlN.

Without losing symmetry, plasmonic Fano resonances have been observed and investigated in multiple nanorod dimers antennae in this paper. The dipole–dipole Fano resonance in three nanorod dimers can be excited simultaneously due to the resonance detuning, and the induced currents of nanorod dimers on both sides are in-phase and out-of-phase with the middle nanorod dimer, respectively. The sharp Fano dip excited in three nanorod dimers antennae can be used to realize the high sensitive sensing of 1116 nm/RIU in the visible and near infrared regions. Furthermore, the Fano resonance is also observed in plasmonic nanoantennae with four nanorod dimers.

The interface quality between III–V semiconductor and high-k material is critical for improving the performance of the metal-oxide-semiconductor field effect transistors. Utilizing first-principles calculations, we explore the electronic properties of the GaAs/HfO₂ interface when indium interfacial atom defects are introduced. The stability of the interfaces will increase with the increasing of the number of indium interfacial atoms. Meanwhile, the band offsets also depend on the number of indium atom substitutions and interstitials. Furthermore, the substitutions suppress the interfacial gap states near the VBM and have the partially passivation, but the effect of interstitial passivation on the interfacial states are limited.

There is a long-standing issue that the optical conductivity in normal-state of cuprate superconductors deviates the conventional Drude type marked by ${\omega }^{-2}$ dependence, exhibiting two main components from underdoping to overdoping, a narrow band peaked around zero energy and a broadband centered in the mid-infrared region called mid-infrared band. Within the renormalized t-J model and self-consistent mean field theory, we discuss the doping and energy dependence of optical conductivity in cuprate superconductors. Our results show that the appearance of the pseudogap in normal state is responsible for anomalous optical conductivity, giving rise to the mid-infrared band. In particular, in analogy to the doping dependence of pseudogap, optical conductivity is also strongly doping dependent. By increasing the doping concentration, the spectral weight of the optical conductivity suppressed strongly in underdoped region increases quickly, and the peak position of the mid-infrared band moves towards to the lower energy region, then incorporates into the narrow band centered in zero energy in the heavily overdoped region.

The surface morphology of ZnO evolving from nanorod to nanoplate is controlled through the increase of Al${}^{3+}$ concentration in aqueous solution. In the process of fabricating ZnO nanoplate, Al${}^{3+}$ acts as surface passivating agent and the growth rate along the [0001] orientation is suppressed. The blueshift of free excitons occurs with the increasing of Al${}^{3+}$ concentration.

We demonstrate the generation of harmonic mode-locking (HML) in an erbium-doped fiber laser with a microfiber-based rhenium disulfide (ReS₂) saturable absorber (SA). Taking advantages of both saturable absorption and large third-order nonlinear effect of ReS₂, HML pulse with 318.5 MHz repetition rate can be obtained, corresponding to 168th harmonic of fundamental repetition frequency of 1.896 MHz. When the pump power is increased gradually, the pulse interval remains constant, while the output power increases linearly. At the pump power of 450 mW, the output power is $\sim$12 mW. The proposed high-repetition-rate pulse lasers would attract considerable attention due to its potential applications in soliton communications and frequency combs.

The absorption characteristics of a photoexcited metamaterial absorber at terahertz frequencies were analyzed in this study. Filling photosensitive semiconductor silicon into the gap between the resonator arms leads to modulation of its electromagnetic response through a pump beam which changes conductivity of silicon. Comparisons of terahertz absorbing properties which were caused by different thicknesses and dielectric constants of polyimide, cell sizes and widths of SRRs, and lengths and conductivities of the photosensitive silicon, were studied by using Finite Difference Time Domain (FDTD) from 0.4 THz to 1.6 THz. The results of this study will facilitate the design and preparation of terahertz modulator, filters and absorbers.