Binding energy of an impurity in polar microspheres

We have examined the binding energy of a polaron bound to a hydrogenic donor impurity located in a spherical quantum dot by means of a variational technique for both finite and infinite potential models. The polaronic effect on the binding energy has been considered taking into account the ion-phonon coupling by using the Lee-Low-Pines variational method. The results we have obtained show that the binding energies are drastically affected by the dot radius, the potential barrier height and the polaronic effects.We have examined the binding energy of a polaron bound to a hydrogenic donor impurity located in a spherical quantum dot by means of a variational technique for both finite and infinite potential models. The polaronic effect on the binding energy has been considered taking into account the ion-phonon coupling by using the Lee-Low-Pines variational method. The results we have obtained show that the binding energies are drastically affected by the dot radius, the potential barrier height and the polaronic effects

Anisotropy of the gap energy in high Tc Copper Oxides

Within the frame work of BCS phonon-mediated pairing with a logarithmic (2D) Van Hove Singularity in the density of states, we study the anisotropy of superconductors gap taking into account the anisotropy of attractive coupling and the coulomb repulsion .The results show that gap is more disperse and can explain some observed experimental data.Within the frame work of BCS phonon-mediated pairing with a logarithmic (2D) Van Hove Singularity in the density of states, we study the anisotropy of superconductors gap taking into account the anisotropy of attractive coupling and the coulomb repulsion .The results show that gap is more disperse and can explain some observed experimental data

Self Consistent RPA applied to the extended Hubbard Model

Using the extended Hubbard model with the Self Consistent Random Phase Approximation (SCRPA), we study the intersite interaction effect on the dynamics of N electrons. We consider the extended Hubbard model containing intrasite and intersite interactions, and we apply this model to a system of two interacting atoms, where each atom presents one free electron. The resolution of this tow sites problem is done by the SCRPA approximation; our calculations allow as studying the intersite interaction effect on the excitation energies of system. We have showed that the attractive interaction between the electrons of the neighbour’s atoms is the origin of supplementary conductivity of the system.Using the extended Hubbard model with the Self Consistent Random Phase Approximation (SCRPA), we study the intersite interaction effect on the dynamics of N electrons. We consider the extended Hubbard model containing intrasite and intersite interactions, and we apply this model to a system of two interacting atoms, where each atom presents one free electron. The resolution of this tow sites problem is done by the SCRPA approximation; our calculations allow as studying the intersite interaction effect on the excitation energies of system. We have showed that the attractive interaction between the electrons of the neighbour’s atoms is the origin of supplementary conductivity of the system

Ballistic heat transport in semiconductors within the extended irreversible thermodynamics theory

The transport in miniaturised electronic devices requires to go beyond simple hydrodynamic descriptions. So, carrier transports in nano-length devices is no longer dominated by collisions among the particles but the ballistic transport governs at this level. This type of transport occurs when the perturbation characteristic time is of the order of the relaxation time and the mean free path is of the order of the device's dimension. The aim of the present work is to calculate the ballistic velocity of heat transport by using a continued-fraction technique in the framework of extended irreversible thermodynamics. This ballistic speed must be less or equal to the maximum value c0 corresponding to phonon speed. Note that the classical Fourier equation is only able to describe the diffusion regime and the Maxwell-Cattaneo equation predicts a second sound propagation at speed c0/Ö3 but it is silent about the ballistic behaviour .The transport in miniaturised electronic devices requires to go beyond simple hydrodynamic descriptions. So, carrier transports in nano-length devices is no longer dominated by collisions among the particles but the ballistic transport governs at this level. This type of transport occurs when the perturbation characteristic time is of the order of the relaxation time and the mean free path is of the order of the device's dimension. The aim of the present work is to calculate the ballistic velocity of heat transport by using a continued-fraction technique in the framework of extended irreversible thermodynamics. This ballistic speed must be less or equal to the maximum value c0 corresponding to phonon speed. Note that the classical Fourier equation is only able to describe the diffusion regime and the Maxwell-Cattaneo equation predicts a second sound propagation at speed c0/Ö3 but it is silent about the ballistic behaviour

Polaron effect on the binding energy of a hydrogenic impurity in GaAs-Ga 1-x Al x As superlattice

The effect of the bulk Longitudinal-Optical (LO) phonon on the binding energy is investigated for a shallow donor impurity in a superlattice in the effective mass approximation by using the variational approach. The results are obtained as a function of parameters which characterize the superlattice and the position of the impurity center. The results show that the bulk Longitudinal-Optical (LO) phonon effect decreases by displacing the impurity from the center to the well boundary.The effect of the bulk Longitudinal-Optical (LO) phonon on the binding energy is investigated for a shallow donor impurity in a superlattice in the effective mass approximation by using the variational approach. The results are obtained as a function of parameters which characterize the superlattice and the position of the impurity center. The results show that the bulk Longitudinal-Optical (LO) phonon effect decreases by displacing the impurity from the center to the well boundary

The effect of confined Longitudinal Optical Phonons on the Binding Energy of an impurity in CdSe Quantum Dot

Using a variational approach, the effect of the confined LO-phonon on the binding energy in CdSe Quantum Dot has been calculated. The charge-carrier-phonon coupling is treated within the adiabatic approximation. Our results show that the effect of the confined LO-phonon on the binding energy decreases with the dot size. However the correction of the confined LO-phonon to bound state energy increases with dot size.Using a variational approach, the effect of the confined LO-phonon on the binding energy in CdSe Quantum Dot has been calculated. The charge-carrier-phonon coupling is treated within the adiabatic approximation. Our results show that the effect of the confined LO-phonon on the binding energy decreases with the dot size. However the correction of the confined LO-phonon to bound state energy increases with dot size

Polaron Effect on the Binding Energy of Shallow Donor in Cylindrical Quantum Dot

In the framework of the effective-mass approximation and the modified Lee-Low-Pines variational method, we present a theoretical study of the effect of the confined longitudinal-optical phonon and two types of surface-optical phonon (top and side mode) on the binding energy of shallow donor in cylindrical quantum dot. The effect of quantum confinement is described by an infinitely deep potential well. The impact of these different phonon modes is important and depends on the dimension of the quantum dot

Using the extended Hubbard model with the Self Consistent Random Phase Approximation (SCRPA),

we study the intersite interaction effect on the dynamics of N electrons. We consider the extended Hubbard model containing intrasite and intersite interactions, and we apply this model to a system of two interacting atoms, where each atom presents one free electron. The resolution of this tow sites problem is done by the SCRPA approximation; our calculations allow as studying the intersite interaction effect on the excitation energies of system. We have showed that the attractive interaction between the electrons of the neighbour’s atoms is the origin of supplementary conductivity of the system