Virulh Sa-yakanit

Two-dimensional electron transport in MgZnO/ZnO heterostructures: role of interface roughness

Mobility of two-dimensional electron gases in MgZnO/ZnO heterostructures with interface roughness effects was investigated theoretically using path-integral framework. We modelled the roughness-induced fluctuation by including two major effects, i.e. the electron and polarization-induced positive charge concentrations. We showed that both effects cause the scattering potential in the in-plane direction and hence affect the 2D mobility. In this work, we treated both electron and polarization-induced positive charge concentrations as equally important factors and then calculated the electron mobility and compared with the experimental result of Mg0.2Zn0.8O/ZnO heterostructure at high-electron concentrations. We found that the fitting parameters Δ = 0.26 nm, Λ = 2.5 nm gave good description to the mobility data. We also showed that neglecting the polarization-induced positive charge concentration led to overestimating the 2D mobility.

Crystallography and optical energy gap values for AgGa(Se1−zTez)2 alloys

Polycrystalline samples of AgGa(Se1−zTez)2 alloys were prepared by a melt‐and‐anneal technique, annealing at 650 °C for up to 4 months being required to give good equilibrium conditions. It was confirmed that single phase solid solution occurs at all values of z and values of lattice parameters a, c, and c/a were determined from Guinier–Haegg powder photographs. Line intensities were obtained from diffractometer measurements and, hence, values of the anion displacement u determined as a function of z. Comparison of these experimental data has been made with the expressions proposed by Abrahams and Bernstein and by Jaffe and Zunger. The values of u from the former equation show rather poor agreement, particularly at the AgGaSe2 end of the composition range. However, the equations of Jaffe and Zunger, used with Phillips radii, give very good agreement for both u and a but poorer agreement for c and c/a. The optical energy gap E0 is found to show a parabolic variation with z. Comparison with seven similar al...

GROUND STATE ENERGY OF BOSE-EINSTEIN CONDENSATION IN A DISORDERED SYSTEM

A modeled Bose system consisting of N particles with two-body interaction confined within volume V under inhomogeneity of the system is investigated using the Feynman path integral approach. The two-body interaction energy is assumed to be dependent on the two-parameter interacting strength a and the correlation length l. The inhomogeneity of the system or the porosity can be represented as density

Bose-Einstein condensation in nonuniform media

\overline{n}

Description of low temperature bandtail states in two-dimensional semiconductors using path integral approach

with interacting strength b and correlation length L. The mean field approximation on the two-body interaction in the Feynman path integrals representation is performed to obtain the one-body interaction. This approximation is equivalent to the Hartree approximation in the many-body electron gas problem. This approximation has shown that the calculation can be reduced to the effective one-body propagator. Performing the variational calculations, we obtain analytical results of the ground state energy which is in agreement with that from Bugoliubovs approach.

Interface roughness effect on density of states and mobility of narrow Si/Si1―xGex quantum wells: path-integral approach

Abstract The Bogoliubov model of a nonideal gas is developed for Bose-Einstein condensation (BEC) in media with broken translational symmetry. A decrease of the transition temperature T λ is found as a function of the ratio F 1 g 0 , where g 0 is the interaction between the atoms of the condensate and F 1 is the condensate-noncondensate interaction, generated by the nonhomogeneous property of the matter. The shift of T λ in porous media experimentally found by Wong et al. [Phys. Rev. Lett. 65 (1990) 2410] is applied to estimate the ratio F 1 g 0 , which is found to be equal to 0.1, and may be considered as a measure of the influence of the porosity on the interaction between the atoms.

Lyotropic Ion Channel Current Model Compared with Ising Model

We used the solutions from the variational path integral to suggest a function form of the bandtail states of a two-dimensional system. The analytic solutions provide two regimes, i.e., the ground state (low temperature) and the semiclassical (high temperature) limits. We used the theoretical results to describe the results of the bandtail states in Si/SiO2 heterostructure reported recently (Jock et al., Appl. Phys. Lett. 100, 023503 (2012)). The low-temperature bandtail provided good agreement to the experimental results (sample B) with the parameters of Δ = 0.225 nm, L = 3.55 nm, and a = 5 nm.

Ligand-gated ion channel currents in a nonstationary lyotropic model

The in-plane transport of a two-dimensional hole gas in narrow Si/Si1?xGex quantum wells (QWs) with the interface roughness effect was investigated using path-integral theory. The random variation of the well width causes the fluctuation potential in the in-plane direction. This fluctuation was integrated into the path integral via the eigenvalue model of the infinite barrier height QW. The hole mobility and the density of states can be derived in an analytic form. The calculated hole mobility was compared with the experimental data and a different theoretical approach based on the wavefunction model. We found that ? = 0.2?nm and ? = 4.5?nm give a good description of the experimental data. Our theory predicted the existence of the localized states, which reduces the hole mobility in addition to the prediction from the wavefunction method.

Bose–Einstein condensation in a disordered system: the Feynman path integral approach

Trans-membrane currents in ligand-gated ion channels are calculated in a non-equilibrium, chemically open whole cell system. The model is lyotropic in the sense that dynamics and parameters such as ligand concentration for half-maximal response (scale of response), and threshold for firing in neurons, are nonlinear functions of the reactant concentrations. The derived total current fits recorded data significantly better than those derived from mass action, Ising, and other equilibrium type models, in which the derived response can be displaced from the assessed response by several orders in the ligand concentration. A comparison of the model obtained with an Ising-like model provides a methodology to obtain the non-equilibrium scaling dependence of Ising-like models on the reactant concentrations.

PATH INTEGRAL AND VARIATION METHOD IN THE BAND TAIL PROBLEM

Transmembrane currents in ligand-gated ion channels are calculated in a nonstationary, chemically open whole cell system or patch of a membrane. The model is lyotropic in the sense that dynamics, and parameters such as the ligand concentration for half-maximal response (scale of response), and threshold for firing, such as in neurons, become nonlinear functions of the reactant concentrations. The derived total currents fit recorded data significantly better than those derived from mass action, Ising, and other stationary type models, in which the derived response is often displaced from the assessed response by several orders in the ligand concentration. Also, the derived slope of response is in perfect agreement with the values assessed.