Physics Open最新文献

We consider a 1D Klein–Fock–Gordon particle in a finite interval, or box. We construct for the first time the most general set of pseudo self-adjoint boundary conditions for the Hamiltonian operator that is present in the first order in time 1D Klein–Fock–Gordon wave equation, or the 1D Feshbach–Villars wave equation. We show that this set depends on four real parameters and can be written in terms of the one-component wavefunction for the second order in time 1D Klein–Fock–Gordon wave equation and its spatial derivative, both evaluated at the endpoints of the box. Certainly, we write the general set of pseudo self-adjoint boundary conditions also in terms of the two-component wavefunction for the 1D Feshbach–Villars wave equation and its spatial derivative, evaluated at the ends of the box; however, the set actually depends on these two column vectors each multiplied by the singular matrix that is present in the kinetic energy term of the Hamiltonian. As a consequence, we found that the two-component wavefunction for the 1D Feshbach–Villars equation and its spatial derivative do not necessarily satisfy the same boundary condition that these quantities satisfy when multiplied by the singular matrix. In any case, given a particular boundary condition for the one-component wavefunction of the standard 1D Klein–Fock–Gordon equation and using the pair of relations that arise from the very definition of the two-component wavefunction for the 1D Feshbach–Villars equation, the respective boundary condition for the latter wavefunction and its derivative can be obtained. Our results can be extended to the problem of a 1D Klein–Fock–Gordon particle moving on a real line with a point interaction (or a hole) at one point.

We propose a new scheme for optical quantum simulation of topological systems: by using optical systems to simulate the variation of eigenstates of topological systems in momentum space, we can obtain the information of topological numbers. In this paper the scheme is applied to the one-dimensional (1D) Su–Schrieffer–Heeger (SSH) model and the two-dimensional (2D) Bernevig–Hughes–Zhang (BHZ) model. In addition, in order to apply our scheme to 2D topological systems, we design a method of calculating topological numbers by line integral. Furthermore, we propose a more effective optical simulation scheme for the 2D topological system: we do the optical simulation around discontinuity points to obtain the vorticity of every discontinuity points and the topological number is just the sum of the vorticity of all discontinuity points.

The solutions to the Dirac equation are obtained in the spin and pseudospin symmetry limits are presented using the parametric Nikiforov-Uvarov (pNU) method with the inversely quadratic Hellman (IQH) potential. In the exact non-relativistic spin symmetry limit, the energy and wave function of the IQH potential are obtained and used to investigate the Shannon information entropy of the system. Numerical results of the relativistic energies of the spin and pseudospin symmetry limits of the Dirac equation with the IQH potential are presented and observed to exhibit degeneracy. Also, the results of the Shannon entropy for six states (n = 0, 1, 2, 3, 4, 5) show that the momentum space wave function and probability density are better localized than the position space wave function. Also, the Bialynicki-Birula and Mycielski (BBM) inequality is verified for the system. Our results are found to be consistent with those previously reported in the literature.

The interaction of radiation with material media is a very active area of research, in particular the interaction with new exotic materials. However, we find several controversies in this field, like the Abraham-Minkowski controversy, or the attribution of angular momentum to quasi-static fields.

In the present work we show that besides the electromagnetic momentum density proportional to Poynting's vector, whose time derivative is force and therefore can produce a torque, there are other momentum densities implied by the macroscopic Maxwell equations transformed into momentum balance equations. These momentum densities are also related to forces and torques. We show in this way that torques like D × E and B × H appear in these balance equations transformed into balance equations of angular momentum. The density D × E was used by Beth [Phys. Rev. 50 115–125 (1936)] to measure the angular momentum of radiation fields in interaction with anisotropic dielectrics. Our analysis show that also static or quasi-static fields carry angular momentum and produce torques when interacting with anisotropic materials.

We have applied the quantum coherence theory to the Jaynes–Cummings model for three types of quenched disorder distribution: uniform, Gaussian, and Cauchy-Lorentz. Under certain conditions, we have observed a beat-damping behavior on the dynamics of the $l_1$-norm of coherence. This phenomenon is more evident for the uniform disorder distribution.

The concept of non-Markovianity in open quantum systems is traditionally associated with the existence of information backflows from the environment to the system. Meanwhile, the mechanisms through which such backflows emerge are still a subject of debate. In this work, we use collision models to study memory effects in the dynamics of a qubit system in contact with a thermal bath made up of few ancillas, in which system-ancilla and ancilla–ancilla interactions are considered. In the single-ancilla limit case, we show that the system–bath information flow exhibits an interesting mixture of chaotic and regular oscillatory behavior, which depends on the interaction probabilities. In parallel, our results clearly indicate that the information backflows decrease when new ancillas are added to the bath, which sheds light on the nature of the Markovian to non-Markovian transition.

The tripartite quantum coherence for spin-$\frac{1}{2}$ and bipartite quantum coherence for spin-1 many-body systems are studied with the quantum renormalization group method to investigate the quantum criticality behaviour of both systems. We find both spin-$\frac{1}{2}$ and spin-1 systems exhibit quantum criticality behaviour after different number of iterations. However, the bipartite quantum coherence for spin-1 system reaches the quantum criticality behaviour in lesser number of iterations than the tripartite quantum coherence for spin-$\frac{1}{2}$ system. The quantum criticality behaviour of both systems is also investigated through non-analytic and the scaling behaviour of quantum coherence. Additionally, quantum correlations and quantum phase transition are observed to be more vigorous with higher spin comparatively to the number of parties (i.e., bipartite, tripartite, multipartite) involved in a quantum correlations.

3D-printing or Additive Manufacturing (AM) has been growing as a rapid manufacturing process for many different applications, with Poly (Lactic Acid) as one of the most used materials for 3D-printing. PLA shows great promise for many applications to achieve the goals of the SDGs due to its biodegradability and biocompatibility but lacks when it comes to mechanical strength and thermal resistance. In this study, microcrystalline cellulose (MCC) fibers were introduced as a reinforcement to PLA. The biocomposite filaments were irradiated in a vacuum to enhance the crosslinking. Gamma-ray irradiation in a vacuum has successfully shown signs of crosslinking by increasing the tensile strength and thermal stability of the biocomposite, indicating an enhancement for PLA/MCC for various applications. On the other hand, changes in thermal properties also indicated that irradiation may reduce the processability of the composite, so it is necessary to study the conditions under which the mechanical properties and processability are compatible.

Inorganic semiconductors and conducting polymers are described by band conduction models with delocalized electrons, whereas small-molecule organic compounds are described by hopping conduction between localized molecular orbitals. However, the latter devices can reproduce fully the characteristics of semiconductor devices. Why are they so different and yet so similar? We will try to answer this question using Category theory and considering the meaning of electrical transport in electronic materials. The meaning of the category theory in physics is to consider different mathematical entities under a common mathematical structure.

In this paper, the basic idea of category theory is first explained in detail using the example of complex impedance, and then four examples of its application are discussed. The derivation of the Mott-Gurney equation and the negative capacitance in OLED are discussed as examples of solving problems by moving to different categories. After those simple examples of formal rewriting from physical entity to mathematical entity, it is shown that electrical connection and electrical contact lead to direct sums and direct products of conducting states, based on the duality concept. We conclude that small-molecule organic compounds are not a mere branch of semiconductors, but rather equal counterparts of semiconductors in duality that are necessary to clarify the origin of the difference and similarity between organic electronics and semiconductor physics. Finally, by considering the electrical responses of OLEDs and OFETs in the immittance category, we show that they can be described under a common operating dynamic and propose a new operating model for OFETs.