The success of a ferroelectric tunnel junction (FTJ) depends on the asymmetry of electron tunneling as given by the tunneling electroresistance (TER) effect. This characteristic is mainly assessed considering three transport mechanisms: direct tunneling, thermionic emission, and Fowler-Nordheim tunneling. Here, by analyzing the effect of temperature on TER, we show that taking into account only these mechanisms may not be enough in order to fully characterize the performance of FTJ devices. We approach the electron tunneling in FTJ with the non-equilibrium Green function (NEGF) method, which is able to overcome the limitations affecting the three mechanisms mentioned above. We bring evidence that the performance of FTJs is also affected by temperature–in a non-trivial way–via resonance (Gamow-Siegert) states, which are present in the electron transmission probability and are usually situated above the barrier. Although the NEGF technique does not provide direct access to the wavefunctions, we show that, for single-band transport, one can find the wavefunction at any given energy and in particular at resonant energies in the system.

We have calculated electronic and optical properties of $\mathrm{Si}∕\mathrm{Be}{\mathrm{Se}}_{0.41}{\mathrm{Te}}_{0.59}$ heterostructures by a semiempirical $s{p}^3{s}^{*}$ tight-binding method. Tight-binding parameters and band bowing of $\mathrm{Be}{\mathrm{Se}}_{0.41}{\mathrm{Te}}_{0.59}$ are considered through a recent model for highly mismatched semiconductor alloys. The band bowing and the measurements of conduction band offset lead to a type II heterostucture for $\mathrm{Si}∕\mathrm{Be}{\mathrm{Se}}_{0.41}{\mathrm{Te}}_{0.59}$ with the conduction band minimum in the Si layer and the valence band maximum in the $\mathrm{Be}{\mathrm{Se}}_{0.41}{\mathrm{Te}}_{0.59}$ layer. The electronic structure and optical properties of various ${\left({\mathrm{Si}}_2\right)}_n∕{\left(\mathrm{Be}{\mathrm{Se}}_{0.41}{\mathrm{Te}}_{0.59}\right)}_m$ [001] superlattices have been considered. Two bands of interface states were found within the band gap of bulk Si. Our calculations indicate that the optical edges are below the fundamental band gap of bulk Si and the transitions are optically allowed.

The boundary integral equation (BIE) method ascertains explicit relations between localized surface phonon and plasmon polariton resonances and the eigenvalues of its associated electrostatic operator. We show that group-theoretical analysis of the Laplace equation can be used to calculate the full set of eigenvalues and eigenfunctions of the electrostatic operator for shapes and shells described by separable coordinate systems. These results not only unify and generalize many existing studies, but also offer us the opportunity to expand the study of phenomena such as cloaking by anomalous localized resonance. Hence, we calculate the eigenvalues and eigenfunctions of elliptic and circular cylinders. We illustrate the benefits of using the BIE method to interpret recent experiments involving localized surface phonon polariton resonances and the size scaling of plasmon resonances in graphene nanodiscs. Finally, symmetry-based operator analysis can be extended from the electrostatic to the full-wave regime. Thus, bound states of light in the continuum can be studied for shapes beyond spherical configurations.

An understanding of the mechanical behavior of polymeric materials is crucial for making advancements in the applications and efficiency of nanocomposites, and encompasses their service life, load resistance, and overall reliability. The present study focused on the prediction of the mechanical behavior of biopolymeric nanocomposites with nano-clays as the nanoadditives, using a new modeling and simulation method based on Comsol Multiphysics software 6.1. This modeling considered the complex case of flake-shaped nano-clay additives that could form aggregates along the polymeric matrix, varying the nanoadditive thickness, and consequently affecting the resulting mechanical properties of the polymeric nanocomposite. The polymeric matrix investigated was biopolyamide 11 (BIOPA11). Several BIOPA11 samples reinforced with three different contents of nano-clays (0, 3, and 10 wt%), and with three different nano-clay dispersion grades (employing three different extrusion screw configurations) were obtained by the compounding extrusion process. The mechanical behavior of these samples was studied by the experimental tensile test. The experimental results indicate an enhancement of Young’s modulus as the nano-clay content was increased from 0 to 10 wt% for the same dispersion grades. In addition, the Young’s modulus value increased when the dispersion rate of the nano-clays was improved, showing the highest increase of around 93% for the nanocomposite with 10 wt% nano-clay. A comparison of the modeled mechanical properties and the experimental measurements values was performed to validate the modeling results. The simulated results fit well with the experimental values of Young’s modulus.