The stability of a strong-coupling singlet optical bipolaron is studied for the first time in two- and three-dimensional parabolic quantum dots using the Landau - Pekar variational method. It is shown that the confining potential of the quantum dot reduces the stability of the bipolaron.

No abstract

No abstract

An all-coupling variational calculation has been performed to explore the formation and stability of a bipolaron in a polar semiconductor quantum dot. It has been shown that quantum confinement in general leads to a broadening of the bipolaron stability region. It has been furthermore shown for the first time that stable bipolarons can exist in realistic parabolic quantum dots of polar semiconductors like GaAs, CdS, CdTe and CdSe if they are fabricated in certain range of sizes. © 2006 Elsevier B.V. All rights reserved

An all-coupling variational calculation based on Lee-Low-Pines-Huybrechts (LLPH) theory is performed to study the ground state and the first excited state in an asymmetric polar semiconductor quantum wire that is valid for the entire range of the electron-phonon coupling constant and arbitrary confinement length. It is shown that the polaronic effects are very important and size dependent, if the effective width of the wire is reduced below a certain length scale. It is also shown that asymmetry in a quantum wire can be used as an extra parameter to increase the stability of the polaron. Finally the theory is applied to a realistic CdS quantum wire.

No abstract

A variational calculation is performed to obtain the polaronic corrections to the ground and the first-excited-state energies of an electron in a parabolic quantum dot of a polar semiconductor for the entire range of the electron-phonon coupling constant and the confinement length. The number of virtual phonons, the size of the polaron and the polarization potential in the polaron ground state are also calculated. The theory is applied to both two- and three-dimensional GaAs quantum dots and it is shown that both the ground and the first-excited-state polaronic corrections in these dots can be considerably large if the dot sizes are of the order a few nanometres.

Dynamics of dissipation of a local phonon distribution to the substrate is a key issue in friction between sliding surfaces as well as in boundary lubrication. We consider a model system consisting of an excited nano-particle which is weakly coupled with a substrate. Using three different methods we solve the dynamics of energy dissipation for different types of coupling between the nano-particle and the substrate, where different types of dimensionality and phonon densities of states were also considered for the substrate. In this paper, we present our analysis of transient properties of energy dissipation via phonon discharge in the microscopic level towards the substrate. Our theoretical analysis can be extended to treat realistic lubricant molecules or asperities, and also substrates with more complex densities of states. We found that the decay rate of the nano-particle phonons increases as the square of the interaction constant in the harmonic approximation.