3,476 research outputs found
Theory of Polar Corrections to Donor Binding
We calculate the optical phonon correction to the binding energy of electrons
to donors in cubic materials. Previous theories calculated the Rydberg energy
reduced by the effective mass and the static dielectric function. They omitted
an important energy term from the long-range polarization of the ionized donor,
which vanishes for the neutral donor. They also omitted the donor-phonon
interaction. Including these terms yields a new formula for the donor binding
energy
Theoretical study of X-ray absorption of three-dimensional topological insulator
X-ray absorption edge singularity which is usually relevant for metals is
studied for the prototype topological insulator .
The generalized integral equation of Nozi\`eres and Dominicis type for X-ray
edge singularity is derived and solved. The spin texture of surfaces states
causes a component of singularity dependent on the helicity of the spin
texture. It also yields another component for which the singularity from
excitonic processes is absent.Comment: RevTeX 4.1. 4 pages, no figur
The thermopower as a fingerprint of the Kondo breakdown quantum critical point
We propose that the thermoelectric power distinguishes two competing
scenarios for quantum phase transitions in heavy fermions : the
spin-density-wave (SDW) theory and breakdown of the Kondo effect. In the Kondo
breakdown scenario, the Seebeck coefficient turns out to collapse from the
temperature scale , associated with quantum fluctuations of the Fermi
surface reconfiguration. This feature differs radically from the physics of the
SDW theory, where no reconstruction of the Fermi surface occurs, and can be
considered as the hallmark of the Kondo breakdown theory. We test these ideas,
upon experimental results for YbRhSi
Decoherence in quantum dots due to real and virtual transitions: a non-perturbative calculation
We investigate theoretically acoustic phonon induced decoherence in quantum
dots. We calculate the dephasing of fundamental (interband or intraband)
optical transitions due to real and virtual transitions with higher energy
levels. Up to two acoustic phonon processes (absorption and/or emission) are
taken into account simultaneously in a non-perturbative manner. An analytic
expression of acoustic phonon induced broadening is given as a function of the
electron-phonon matrix elements and is physically interpreted. The theory is
applied to the dephasing of intersublevel transitions in self-assembled quantum
dots.Comment: 8 pages, 4 figure
Dielectric function, screening, and plasmons in 2D graphene
The dynamical dielectric function of two dimensional graphene at arbitrary
wave vector and frequency , , is calculated in
the self-consistent field approximation. The results are used to find the
dispersion of the plasmon mode and the electrostatic screening of the Coulomb
interaction in 2D graphene layer within the random phase approximation. At long
wavelengths () the plasmon dispersion shows the local classical
behavior , but the density dependence of the
plasma frequency () is different from the usual 2D
electron system (). The wave vector dependent plasmon
dispersion and the static screening function show very different behavior than
the usual 2D case.Comment: 6 pages, 3 figure
Nonlinear photon transport in a semiconductor waveguide-cavity system containing a single quantum dot: Anharmonic cavity-QED regime
We present a semiconductor master equation technique to study the
input/output characteristics of coherent photon transport in a semiconductor
waveguide-cavity system containing a single quantum dot. We use this approach
to investigate the effects of photon propagation and anharmonic cavity-QED for
various dot-cavity interaction strengths, including weakly-coupled,
intermediately-coupled, and strongly-coupled regimes. We demonstrate that for
mean photon numbers much less than 0.1, the commonly adopted weak excitation
(single quantum) approximation breaks down, even in the weak coupling regime.
As a measure of the anharmonic multiphoton-correlations, we compute the Fano
factor and the correlation error associated with making a semiclassical
approximation. We also explore the role of electron--acoustic-phonon scattering
and find that phonon-mediated scattering plays a qualitatively important role
on the light propagation characteristics. As an application of the theory, we
simulate a conditional phase gate at a phonon bath temperature of K in the
strong coupling regime.Comment: To appear in PR
Self-localization of a small number of Bose particles in a superfluid Fermi system
We consider self-localization of a small number of Bose particles immersed in
a large homogeneous superfluid mixture of fermions in three and one dimensional
spaces. Bosons distort the density of surrounding fermions and create a
potential well where they can form a bound state analogous to a small polaron
state. In the three dimensional volume we observe the self-localization for
repulsive interactions between bosons and fermions. In the one dimensional case
bosons self-localize as well as for attractive interactions forming, together
with a pair of fermions at the bottom of the Fermi sea, a vector soliton. We
analyze also thermal effects and show that small non-zero temperature affects
the pairing function of the Fermi-subsystem and has little influence on the
self-localization phenomena.Comment: 7 pages, 7 fiqures, improved versio
Phonon-dressed Mollow triplet in the regime of cavity-QED
We study the resonance fluorescence spectra of a driven quantum dot placed
inside a high semiconductor cavity and interacting with an acoustic phonon
bath. The dynamics is calculated using a time-convolutionless master equation
obtained in the polaron frame. We demonstrate pronounced spectral broadening of
the Mollow sidebands through cavity-emission which, for small cavity-coupling
rates, increases quadratically with the Rabi frequency. However, for larger
cavity coupling rates, this broadening dependence is found to be more complex.
This field-dependent Mollow triplet broadening is primarily a consequence of
the triplet peaks sampling different parts of the asymmetric phonon bath, and
agrees directly with recent experiments with semiconductor micropillars. The
influence from the detuned cavity photon bath and multi-photon effects is shown
to play a qualitatively important role on the fluorescence spectra.Comment: 4 pages, 4 figure
Polaronic features in the optical properties of the Holstein-t-J model
We derive the exact solution for the optical conductivity of
one hole in the Holstein-t-J model in the framework of dynamical mean-field
theory (DMFT). We investigate the magnetic and phonon features associated with
polaron formation as a function of the exchange coupling , of the
electron-phonon interaction and of the temperature. Our solution
directly relates the features of the optical conductivity to the excitations in
the single-particle spectral function, revealing two distinct mechanisms of
closing and filling of the optical pseudogap that take place upon varying the
microscopic parameters. We show that the optical absorption at the polaron
crossover is characterized by a coexistence of a magnon peak at low frequency
and a broad polaronic band at higher frequency. An analytical expression for
valid in the polaronic regime is presented.Comment: improved version, as submitted to Phys. Rev.
Device for preventing high voltage arcing in electron beam welding Patent
Development of device to prevent high voltage arcing in electron beam weldin
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