Modern Physics Letters B

Interaction of metal atoms with organic thin films is a fundamental issue in the optimization performances of novel devices. The computational investigations, based on density functional theory, reveal that a realistic description of the reactive processes is obtained when the organic thin film is modeled by its crystallographic structure. In this case, the metal atoms can react with multiple organic molecules present in the solid forming complexes where they are bound both to O atoms and to aromatic C atoms of the molecules. Calculated band gap states, induced by chemical reaction upon deposition, reproduce quite well the measured density of states as a function of the metal concentration in the solid. Simulated core level shift spectra for N(1s), O(1s) and Al (2p) in doped systems are in good agreement with experimental spectra and the electronic structure analysis provides a microscopic description of reaction processes. Interestingly, K atoms in PTCDA solid are ionically bound to anhydride O atoms and are able to form quasi mono-dimensional chain along the stack direction of the organic material.

Two new azo-dye chromophores containing different electron-acceptor groups were synthesized and characterized by ¹H NMR, FT-IR and UV-vis spectra, respectively. The second-order nonlinearity of azo-dyes doped films in poly (methylmethacrylate) and the first hyperpolarizability of the azo molecules were investigated by the Maker Fringe method and the solvatochromic method, respectively. Experimental results showed that both of the two dyes exhibited large second-order nonlinearity (d₃₃ > 30 pm/v) and the stronger electron-acceptor groups in dye molecules would induce larger second-order nonlinearity. This was confirmed by the measurement of the first hyperpolarizability.

Based on the technique of integration within an ordered product of nonlinear Bose operators, a new kind of nonlinear coherent entangled state, which exhibits both the property of coherent state and quantum entanglement, is constructed and its application in squeezing is discussed.

A simple and explicit formula for specific heat of icoschedral Al-Mn-Pd quasicrystals is obtained, theoretical predictions of which are in good agreement with that given by experiment.

The quantum transport of electrons through a three-lead ballistic Aharonov–Bohm (AB) ring with the Rashba spin-orbit interaction is revisited in terms of the S-matrix method from which the transmission probabilities are obtained analytically. It is shown that this mesoscopic device indeed can act as a spin-filter resulting in a relative spin-rotation between the input and output states while can act as a spin polarizer or splitter for a completely unpolarized, mixture input-state. In contrast with the result of Griffith's boundary conditions, the backscattering of carriers on the junction does not allow this three-terminal device to have unit efficiency. In addition, we point out that the AB ring with two symmetrically situated output leads also can give rise to the redistribution of the outgoing currents with respect to the variation of magnetic flux.

We construct 2N operators for a N-particle system, namely one center-of-mass coordinate operator, N-1 relative coordinate operators, one total momentum operator and N-1 mass-weighted relative momentum operators, and give common eigenvectors of N compatible observables , which are composed of N particles' coordinate and momentum . By compatible, we mean such observables can be simultaneously determined. Using the technique of integration within an ordered product of operators (IWOP), we prove that the common eigenvectors are complete and orthonormal, and hereby qualified for making up a representation. This new representation can be applied to solving some dynamic problems in quantum mechanics.

The study of thin ferromagnetic films has become a field of great interest due to their importance for applications in magnetic-recording media, in order to create ultrahigh density magnetic data storage. Such an interest is also due to numerous specific phenomena related to the low dimension of these systems. In this paper we investigate the magnetic properties of bilayer thin film. The specific behavior of the mentioned system type is simulated using the Monte Carlo technique, in the extended anisotropic Heisenberg model. The magnetization, out-of-plane and in-plane magnetic susceptibilities behaviors according to temperature are investigated in order to find out the contingent magnetic ordering phase and the critical temperature, for two easy-axis anisotropy set parameter assignments. We have also presented the specific heat as a function of temperature for different direct exchange parameter values and we have found out a single-peak shape of the graphs, the critical point traveling to lower temperatures as the direct exchange parameter decreases, the similarity of the two presented cases being evident.

An ensemble Monte Carlo simulation is used to compare high field electron transport in bulk InAs, InP and GaAs. In particular, velocity overshoot and electron transit times are examined. For all materials, we find that electron velocity overshoot only occurs when the electric field is increased to a value above a certain critical field, unique to each material. This critical field is strongly dependent on the material, about 400 kVm^-1 for the case of GaAs, 300 kVm^-1 for InAs and 700 kVm^-1 for InP. We find that InAs exhibits the highest peak overshoot velocity and that this velocity overshoot lasts over the longest distances when compared with GaAs and InP. Finally, we estimate the minimum transit time across a 1 μm GaAs sample to be a bout 3 ps. Similar calculations for InAs and InP yield 2.2 and 5 ps, respectively. The steady-state and transient velocity overshoot characteristics are in fair agreement with other recent calculations.