1,404 research outputs found
Temperature dependence of the angle resolved photoemission spectra in the undoped cuprates: self-consistent approach to the t-J-Holstein model
We develop a novel self-consistent approach for studying the angle resolved
photoemission spectra (ARPES) of a hole in the t-J-Holstein model giving
perfect agreement with numerically exact Diagrammatic Monte Carlo data at zero
temperature for all regimes of electron-phonon coupling. Generalizing the
approach to finite temperatures we find that the anomalous temperature
dependence of the ARPES in undoped cuprates is explained by cooperative
interplay of coupling of the hole to magnetic fluctuations and strong
electron-phonon interaction.Comment: 5 pages, 4 figure
Mesoscopic continuous and discrete channels for quantum information transfer
We study the possibility of realizing perfect quantum state transfer in
mesoscopic devices. We discuss the case of the Fano-Anderson model extended to
two impurities. For a channel with an infinite number of degrees of freedom, we
obtain coherent behavior in the case of strong coupling or in weak coupling
off-resonance. For a finite number of degrees of freedom, coherent behavior is
associated to weak coupling and resonance conditions
Collective excitations and low temperature transport properties of bismuth
We examine the influence of collective excitations on the transport
properties (resistivity, magneto- optical conductivity) for semimetals,
focusing on the case of bismuth. We show, using an RPA approximation, that the
properties of the system are drastically affected by the presence of an
acoustic plasmon mode, consequence of the presence of two types of carriers
(electrons and holes) in this system. We found a crossover temperature T*
separating two different regimes of transport. At high temperatures T > T* we
show that Baber scattering explains quantitatively the DC resistivity
experiments, while at low temperatures T < T* interactions of the carriers with
this collective mode lead to a T^5 behavior of the resistivity. We examine
other consequences of the presence of this mode, and in particular predict a
two plasmon edge feature in the magneto-optical conductivity. We compare our
results with the experimental findings on bismuth. We discuss the limitations
and extensions of our results beyond the RPA approximation, and examine the
case of other semimetals such as graphite or 1T-TiSe_2
Dual quantum-correlation paradigms exhibit opposite statistical-mechanical properties
We report opposite statistical mechanical behaviors of the two major
paradigms in which quantum correlation measures are defined, viz., the
entanglement-separability paradigm and the information-theoretic one. We show
this by considering the ergodic properties of such quantum correlation measures
in transverse quantum XY spin-1/2 systems in low dimensions. While entanglement
measures are ergodic in such models, the quantum correlation measures defined
from an information-theoretic perspective can be nonergodic.Comment: 8 pages, 5 figures, REVTeX 4.1; v2: published version, 9 page
Artifact of the phonon-induced localization by variational calculations in the spin-boson model
We present energy and free energy analyses on all variational schemes used in
the spin-boson model at both T=0 and . It is found that all the
variational schemes have fail points, at where the variational schemes fail to
provide a lower energy (or a lower free energy at ) than the
displaced-oscillator ground state and therefore the variational ground state
becomes unstable, which results in a transition from a variational ground state
to a displaced oscillator ground state when the fail point is reached. Such
transitions are always misidentied as crossover from a delocalized to localized
phases in variational calculations, leading to an artifact of phonon-induced
localization. Physics origin of the fail points and explanations for different
transition behaviors with different spectral functions are found by studying
the fail points of the variational schemes in the single mode case.Comment: 9 pages, 7 figure
Many-body Green's function approach to attosecond nonlinear X-ray spectroscopy
Closed expressions are derived for resonant multidimensional X-ray
spectroscopy using the quasiparticle nonlinear exciton representation of
optical response. This formalism is applied to predict coherent four wave
mixing signals which probe single and two core-hole states. Nonlinear X-ray
signals are compactly expressed in terms of one- and two- particle Green's
functions which can be obtained from the solution of Hedin-like equations at
the level.Comment: 10 pages and 3 figures (To appear in Physical Review B
Prerequisite for superconductivity: appropriate spin-charge correlations
This work investigates the relation between superconductivity and
correlations. A simple calculation shows that the appropriate spin-charge
correlation is the key role to any superconductivity, and this calculation is
consistent with the analyses of unusual properties of superconductors. (Note:
the Tc of this model is not given clearly in this work, but we have advanced
this mechanism to a t-x model which includes various superconductivities and
magnetisms (please see arXiv:0707.3660 and following works).)Comment: 7page
Plasmon assisted transport through disordered array of quantum wires
Phononless plasmon assisted thermally activated transport through a long
disordered array of finite length quantum wires is investigated analytically.
Generically strong electron plasmon interaction in quantum wires results in a
qualitative change of the temperature dependence of thermally activated
resistance in comparison to phonon assisted transport. At high temperatures,
the thermally activated resistance is determined by the Luttinger liquid
interaction parameter of the wires.Comment: 7 pages, 1 figure, final version as publishe
Optical properties and one-particle spectral function in non-ideal plasmas
A basic concept to calculate physical features of non-ideal plasmas, such as
optical properties, is the spectral function which is linked to the
self-energy. We calculate the spectral function for a non-relativistic hydrogen
plasma in -approximation. In order to go beyond approximation, we
include self-energy and vertex correction to the polarization function in
lowest order. Partial compensation is observed. The relation of our approach to
and calculations in other fields, such as the band-structure
calculations in semiconductor physics, is discussed. From the spectral function
we derive the absorption coefficient due to inverse bremsstrahlung via the
polarization function. As a result, a significant reduction of the absorption
as compared to the Bethe-Heitler formula for bremsstrahlung is obtained.Comment: 13 pages, 7 figures, 52 references. Submitted to Contrib. Plasma
Phys. Results presented at the International Workshop on Physics of Non-ideal
Plasmas (PNP12), Darmstadt, sept. 4.-8. 200
A Non-equilibrium STM model for Kondo Resonance on surface
Based on a no-equilibrium STM model, we study Kondo resonance on a surface by
self-consistent calculations. The shapes of tunneling spectra are dependent on
the energy range of tunneling electrons. Our results show that both
energy-cutoff and energy-window of tunneling electrons have significant
influence on the shapes of tunneling spectra. If no energy-cutoff is used, the
Kondo resonances in tunneling spectrum are peaks with the same shapes in the
density of state of absorbed magnetic atoms. This is just the prediction of
Tersoff theory. If we use an energy cutoff to remove high-energy lectrons, a
dip structure will modulate the Kondo resonance peak in the tunneling spectrum.
The real shape of Kondo peak is the mixing of the peak and dip, the so-called
Fano line shape. The method of self-consistent non-equilibrium matrix Green
function is discussed in details.Comment: 11 pages and 8 eps figur
- …