35 research outputs found
Exactly solvable toy models of unconventional magnetic alloys: Bethe Ansatz versus Renormalization Group method
We propose toy models of unconventional magnetic alloys, in which the density
of band states, , and hybridization, , are energy
dependent; it is assumed, however, that
, and hence an effective
electron-impurity coupling is
energy independent. In the renormalization group approach, the physics of the
system is assumed to be governed by only rather than by
separate forms of and . However, an exact Bethe
Ansatz solution of the toy Anderson model demonstrates a crucial role of a form
of inverse band dispersion .Comment: A final version. A previous one has been sent to Archive because of
my technical mistake. Sorr
Emission Spectrum of a Dipole in a Semi-infinite Periodic Dielectric Structure: Effect of the Boundary
The emission spectrum of a dipole embedded in a semi-infinite photonic
crystal is calculated. For simplicity we study the case in which the dielectric
function is sinusoidally modulated only along the direction perpendicular to
the boundary surface plane. In addition to oscillations of the emission rate
with the distance of the dipole from the interface we also observed that the
shape of the emission spectrum srongly depends on the \em initial \em phase
of the dielectric modulation. When the direction of light propagation inside
the periodic structure is not normal to the boundary surface plane we observed
aditional singularities in the emission spectrum, which arise due to different
angle-dependence of the Bragg stop-band for and polarizations.Comment: 14 pages, 6 figures, to appear in Phys Rev
Probing Interband Coulomb Interactions in Semiconductor Nanocrystals with 2D Double-Quantum Coherence Spectroscopy
Using previously developed exciton scattering model accounting for the
interband, i.e., exciton-biexciton, Coulomb interactions in semiconductor
nanocrystals (NCs), we derive a closed set of equations for 2D double-quantum
coherence signal. The signal depends on the Liouville space pathways which
include both the interband scattering processes and the inter- and intraband
optical transitions. These processes correspond to the formation of different
cross-peaks in the 2D spectra. We further report on our numerical calculations
of the 2D signal using reduced level scheme parameterized for PbSe NCs. Two
different NC excitation regimes considered and unique spectroscopic features
associated with the interband Coulomb interactions are identified.Comment: 11 pages, 5 figure
Impact of uniaxial strain and doping on oxygen diffusion in CeO2
Doped ceria is an important electrolyte for solid oxide fuel cell applications. Molecular dynamics simulations have been used to investigate the impact of uniaxial strain along the directions and rare-earth doping (Yb, Er, Ho, Dy, Gd, Sm, Nd, and La) on oxygen diffusion. We introduce a new potential model that is able to describe the thermal expansion and elastic properties of ceria to give excellent agreement with experimental data. We calculate the activation energy of oxygen migration in the temperature range 900-1900K for both unstrained and rare-earth doped ceria systems under tensile strain. Uniaxial strain has a considerable effect in lowering the activation energies of oxygen migration. A more pronounced increase in oxygen diffusivities is predicted at the lower end of the temperature range for all the dopants considered