38 research outputs found
Hidden Integrability of a Kondo Impurity in an Unconventional Host
We study a spin-1/2 Kondo impurity coupled to an unconventional host in which
the density of band states vanishes either precisely at (``gapless'' systems)
or on some interval around the Fermi level (``gapped''systems). Despite an
essentially nonlinear band dispersion, the system is proven to exhibit hidden
integrability and is diagonalized exactly by the Bethe ansatz.Comment: 4 pages, RevTe
Temperature and size-dependent suppression of Auger recombination in quantum-confined lead salt nanowires
Auger recombination (AR) of the ground biexciton state in quantum-confined
lead salt nanowires (NWs) with a strong coupling between the conduction and the
valence bands is shown to be strongly suppressed, and only excited biexciton
states contribute to Auger decay. The AR rate is predicted to be greatly
reduced when temperature or the NW radius are decreased, and the effect is
explained by decrease in both the population of excited biexciton states and
overlap of phonon-broadened single- and biexciton states. Suppression of AR of
multiexciton states exhibiting strong radiative decay makes obviously lead salt
NWs a subject of special interest for numerous lasing applications.Comment: 4 pages, 3 figure
Exactly Solvable Model of Superconducting Magnetic Alloys
A model describing the Anderson impurity in the Bardeen-Cooper-Schriffer
superconductor is proven to exhibit hidden integrability and is diagonalized
exactly by the Bethe ansatz.Comment: 10 pages, RevTEX, Phys. Lett. A. (in press
Electronic structure and optical properties of quantum confined lead-salt nanowires
In the framework of four-band envelope-function formalism, developed earlier
for spherical semiconductor nanocrystals, we study the electronic structure and
optical properties of quantum-confined lead-salt (PbSe and PbS) nanowires (NWs)
with a strong coupling between the conduction and the valence bands. We derive
spatial quantization equations, and calculate numerically energy levels of
spatially quantized states of a transverse electron motion in the plane
perpendicular to the NW axis, and electronic subbands developed due to a free
longitudinal motion along the NW axis. Using explicit expressions for
eigenfunctions of the electronic states, we also derive analytical expressions
for matrix elements of optical transitions and study selection rules for
interband absorption.
Next we study a two-particle problem with a conventional long-range Coulomb
interaction and an interparticle coupling via medium polarization. The obtained
results show that due to a large magnitude of the high-frequency dielectric
permittivity of PbSe material, and hence, a high dielectric NW/vacuum contrast,
the effective coupling via medium polarization significantly exceeds the
effective direct Coulomb coupling at all interparticle separations along the NW
axis. Furthermore, the strong coupling via medium polarization results in a
bound state of the longitudinal motion of the lowest-energy electron-hole pair
(a longitudinal exciton), while fast transverse motions of charge carriers
remain independent of each other.Comment: Some misprints and mistakes are correcte
Ground State Properties of Anderson Impurity in a Gapless Host
Using the Bethe ansatz method, we study the ground state properties of a
Anderson impurity in a ``gapless'' host, where a density of band
states vanishes at the Fermi level as . As
in metals, the impurity spin is proven to be screened at arbitrary parameters
of the system. However, the impurity occupancy as a function of the bare
impurity energy is shown to acquire novel qualitative features which
demonstrate a nonuniversal behavior of the system. The latter explains why the
Kondo screening is absent (or exists only at quite a large electron-impurity
coupling) in earlier studies based on scaling arguments.Comment: 5 pages, no figure, RevTe