Karen A. Vardanyan

Confined acoustic phonon-mediated spin relaxation in a twodimensional quantum dot in the presence of perpendicular magnetic field

The spin-relaxation time due to the electron-acoustic phonon scattering in GaAs quantum dots is studied after the exact diagonalization of the electron Hamiltonian with the spin-orbit coupling. It has been shown that in comparison with flexural phonons, the electron coupling with the dilatational phonons causes 3 orders faster spin relaxation. We have found that the relaxation rate of the spin-flip is an order of magnitude smaller than that of the spin- conserving.

The influence of electric field on the quasi-confined and interface polaron basic parameters in a wurtzite nitride quantum wire

The influence of an external electric field on the quasi-confined and interface Frohlich polaron basic parameters in a wurtzite nitride cylindrical quantum wire embedded in a non-polar matrix is studied theoretically. By using the Lee-Low-Pines variational approach, the dependences of the polaron self-energy and effective mass are obtained as functions of the wire radius and the strength of the electric field. The contributions of different phonon modes to the polaron basic parameters are estimated.

Electron capture processes in quantum dots due to one-and two-phonon assisted transitions: The role of optical phonon confinement

Electron capture induced by carrier heating in spherical quantum dot-quantum well (QD-QW) structure is studied theoretically. The capture rate (CR) in one- and two-polar- optical-phonon-mediated capture processes has been studied by taking into account the phonon confinement. We have derived the analytic expressions for carrier CRs which can be conveniently applied to practical calculations for the spherical quantum dot systems. The numerical results of the CR as function of dot radius, lattice temperature and electron density in GaAs/AlAs/vacuum and CdSe/ZnS/H2O QD systems are obtained and discussed.

Effect of Phonon Confinement on Optical Phonon-Mediated Carrier Capture into CdSe/ZnS Quantum Dots

Electron capture induced by carrier heating in the CdSe/ZnS spherical quantum dot–quantum well structure is studied theoretically. The capture rate has been calculated by taking into account the phonon confinement effect. Numerical results for the capture rate as a function of dot radius, lattice temperature, and electron density in the CdSe/ZnS/H2O quantum dot (QD) system are obtained and discussed. It has been shown that the capture rate of an electron from the barrier region to the quantum dot ground state due to the emission of confined or interface optical phonons exhibits strong resonances versus dot radius. Our results reveal that the capture time is larger than 1 ns across broad ranges of quantum dot radius. We have found the increase of the capture rate due to emission of LO1 as well as IO/SO phonons with increasing temperature. However, for structures with lower electron densities (n ≤ 1016 cm−3), the monotonic behavior of the capture rate in case of IO/SO phonon interactions is broken and a local maximum in the temperature dependence appears. In contrast to the GaAs/AlAs spherical quantum dot–quantum well structure, the capture rate in CdSe/ZnS/H2O QDs is very strongly dependent on the electron density.