4,417 research outputs found
Non-local composite spin-lattice polarons in high temperature superconductors
The non-local nature of the polaron formation in t-t'-t"-J model is studied
in large lattices up to 64 sites by developing a new numerical method. We show
that the effect of longer-range hoppings t' and t" is a large anisotropy of the
electron-phonon interaction (EPI) leading to a completely different influence
of EPI on the nodal and antinodal points in agreement with the experiments.
Furthermore, nonlocal EPI preserves polaron's quantum motion, which destroys
the antiferromagnetic order effectively, even at strong coupling regime,
although the quasi-particle weight in angle-resolved-photoemission spectroscopy
is strongly suppressed.Comment: 5 pages, 4 figure
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
Optical signatures of exciton-polarons from diagrammatic Monte Carlo
We study the interplay of electron-electron and electron-phonon interactions
in the course of electron-hole bound state formation for gapped solid state
systems. Adapting the essentially approximation-free diagrammatic Monte Carlo
method for the calculation of the optical response, we discuss the absorption
of light in correlated electron-phonon systems for the whole interaction and
phonon frequency regimes. The spectral function obtained by analytical
continuation from the imaginary-time current-current correlation function
demonstrates the dressing of excitons by a phonon cloud when the coupling the
lattice degrees of freedom becomes increasingly important, where notable
differences show up between the adiabatic and anti-adiabatic cases.Comment: 6 pages, 5 figure
Search for charginos nearly mass-degenerate with the lightest neutralino collisions up to = 209GeV
Search for chargino nearly mass-degenerate with the lightest neutralino is performed with the data collected at a centre-of-mass energy from 189 to 209~GeV by the ALEPH detector at LEP. The analysis uses the detection of an isolated and energetic initial state radiation photon, produced in association with the chargino pair, whose decay products have small visible energy. No evidence of signal is found and lower limits on the chargino mass of 91 and 89~GeV/ at 95\% confidence level are derived, for large scalar masses, in gaugino and in higgsino region respectively
Topological quantum transition driven by charge-phonon coupling in the Haldane Chern insulator
In condensed matter physics many features can be understood in terms of their
topological properties. Here we report evidence of a topological quantum
transition driven by the charge-phonon coupling in the spinless Haldane model
on a honeycomb lattice, a well-known prototypical model of Chern insulator.
Starting from parameters describing the topological phase in the bare Haldane
model, we show that the increasing of the strength of the charge lattice
coupling drives the system towards a trivial insulator. The average number of
fermions in the Dirac point, characterized by the lowest gap, exhibits a finite
discontinuity at the transition point and can be used as direct indicator of
the topological quantum transition. Numerical simulations show, also, that the
renormalized phonon propagator exhibits a two peak structure across the quantum
transition, whereas, in absence of the mass term in the bare Hadane model,
there is indication of a complete softening of the effective vibrational mode
signaling a charge density wave instability.Comment: 5 pages, 4 figure
Two channel model for optical conductivity of high mobility organic crystals
We show that the temperature dependence of conductivity of high mobility
organic crystals Pentacene and Rubrene can be quantitatively described in the
framework of the model where carriers are scattered by quenched local
impurities and interact with phonons by Su-Schrieffer-Hegger (SSH) coupling.
Within this model, we present approximation free results for mobility and
optical conductivity obtained by world line Monte Carlo, which we generalize to
the case of coupling both to phonons and impurities. We find fingerprints of
carrier dynamics in these compounds which differ from conventional metals and
show that the dynamics of carriers can be described as a superposition of a
Drude term representing diffusive mobile particles and a Lorentz term
associated with dynamics of localized charges.Comment: 6 pages, 5 figure
Quantum Dynamics of the Hubbard-Holstein Model in Equilibrium and Non-Equilibrium: Application to Pump-Probe Phenomena
The spectral response and physical features of the 2D Hubbard-Holstein model
are calculated both in equilibrium at zero and low chemical dopings, and after
an ultra short powerful light pulse, in undoped systems. At equilibrium and at
strong charge-lattice couplings, the optical conductivity reveals a 3-peak
structure in agreement with experimental observations. After an ultra short
pulse and at nonzero electron-phonon interaction, phonon and spin subsystems
oscillate with the phonon period fs. The decay time of the
phonon oscillations is about 150-200 fs, similar to the relaxation time of the
charge system. We propose a criterion for observing these oscillations in high
compounds: the time span of the pump light pulse has to be
shorter than the phonon oscillation period .Comment: 4 pages, 4 figure
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