Narrow Results

The binding energy of a bound polaron in an anisotropic quantum dot (QD) subject to electric and magnetic fields along the growth axis has been investigated by using a variational method of Pekar type, taking into account the electron-bulk LO-phonon interaction. The results show that the binding energy decreases with increasing electric field strength and increases with increasing confinement strengths in the lateral and the longitudinal direction, the magnetic field strength, and the Coulomb potential.

The effect of the electron–phonon interaction on an electron bound to a hydrogenic impurity in a three-dimensional (3D) anisotropic quantum dot (QD) is studied theoretically. We use the Landau–Pekar variational approach to calculate the binding energy of ground state (GS) and first-excited state (ES) with considering electron–phonon interaction. The expressions of the GS and ES energies under investigation depict a rich variety of dependent relationship with the variational parameters in three different limiting cases. Numerical calculations were performed for ZnSe QDs with different confinement lengths in the xy-plane and the z-direction, respectively. It is illustrated that binding energies of impurity polarons corresponding to each level are larger in small QDs. Furthermore, the contribution to binding energy from phonon is about 15% of the total binding energy.

The first-excited-state (ES) binding energy of hydrogenic impurity bound polaron in an anisotropic quantum dot (QD) is obtained by constructing a variational wavefunction under the action of a uniform external electric field. As for a comparison, the ground-state (GS) binding energy of the system is also included. We apply numerical calculations to KBr QD with stronger electron–phonon (E–P) interaction in which the new variational wavefunction is adopted. We analyzed specifically the effects of electric field and the effects of both the position of the impurity and confinement lengths in the xy-plane and the $z$ direction on the ground and the first-ES binding energies (BEs). The results show that the selected trial wavefunction in the ES is appropriate and effective for the current research system.

The effect of hydrostatic pressure on binding energy and polaron effect of the bound polaron in a wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N parabolic quantum well (QW) is studied using the Lee–Low–Pines intermediate coupling variational method in the paper. The numerical relationship of binding energy and polaron effect of the bound polaron are given as a functions of pressure $p$, composition $x$ and well width $d$. In the theoretical calculations, the anisotropy of the electron effective band mass, the optical phonon frequency, the dielectric constant and other parameters in the system varying with the pressure $p$ and the coordinate $z$ are included. The electron–optical phonon interaction and the impurity center–optical phonon interaction are considered. The results show that hydrostatic pressure has a very obvious effect on binding energy and polaron effect of the bound polaron in the wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N parabolic QW. For QWs with determined structural parameters, the contributions of the three branch of phonons, i.e., the confined (CF) phonon, half-space (HS) phonon and the interface (IF) phonon, to binding energy of the polaron increase with the increase of the pressure $p$, the CF phonons contribute the most. Under the condition of a certain well width and hydrostatic pressure, with the increase of the composition $x$, the ground state binding energy of the bound polaron in the wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N parabolic QW increases, and the contribution of the IF phonon and HS phonons to the binding energy decreases, while the contribution of the CF phonons and the total contribution of all phonons increase significantly. In the wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_{0.3}$Ga${}_{0.7}$N parabolic QW, the ground state binding energy of the bound polaron decreases with the increase of the well width. The decrease rate is greater in the narrow well, and smaller in the wide well. The contribution of different branches of phonons to binding energy varies with the change of the well width. With the increase of the well width, the contribution of CF phonons to binding energy increases, the contribution of HS phonons to binding energy decreases, and the IF phonon contribution and the total phonon contribution first increase to the maximum value and then gradually decrease slightly. The changing trend of binding energy of bound polaron in the wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N parabolic QW, of the contribution of different branch phonons to binding energy with the pressure $p$, composition $x$ and well width $d$ is similar to that of the GaN/Al${}_x$Ga${}_{1-x}$N square QW, but the change in the parabolic QW is more obvious.

A variational method is used to investigate the binding energies of bound polarons near the interface in a GaAs/Al_xGa_1-xAs heterojunction by considering the hydrostatic pressure effect. It is found that the comprehensive pressure effect on the heterojunction factors increases the binding energies near linearly. The pressure influence on the binding energy for the impurity located on the channel side is stronger than that for the impurity located on the barrier side. The pressure effect is more obvious when the impurity is located on the channel side and is not so far from the interface. The pressure influences on the longitudinal optical phonons and interface optical phonons are discussed.

We study the temperature effect of bound polaron, which is strongly coupled to LO-phonon by using a variational method of the Pekar type in a triangular potential quantum dot (QD). The ground state energy was expressed as functions of the confinement length of QD, the Coulomb bound potential, the polar angle and the temperature. It is found that at low temperature, the influence of Coulomb bound potential and the confinement length of QD to the ground state energy of bound polaron play a leading role. At high temperature, the influence of temperature to the ground state energy of bound polaron is dominant.

The effect of phonon confinement on ground state binding energy of bound polaron in polar quantum wires with a finite confining potential investigated by Landau-Pekar variation technique. The effect of external electric and magnetic fields is taken into account as well. The obtained results show that the polar optical phonon confinement leads to a considerable enhancement of the polaron effect and these corrections increase with increasing of applied fields.