2,112 research outputs found
Odd parity charge density-wave scattering in cuprates
We investigate a model where superconducting electrons are coupled to a
frequency dependent charge-density wave (CDW) order parameter Delta(w). Our
approach can reconcile the simultaneous existence of low energy Bogoljubov
quasiparticles and high energy electronic order as observed in scanning
tunneling microscopy (STM) experiments. The theory accounts for the contrast
reversal in the STM spectra between positive and negative bias observed above
the pairing gap. An intrinsic relation between scattering rate and
inhomogeneities follows naturally.Comment: 5 pages, 3 figure
Interplay between density and superconducting quantum critical fluctuations
We consider the case of a density-driven metal-superconductor transition in
the proximity of an electronic phase separation. In particular we investigate
the interplay between superconducting fluctuations and density fluctuations,
which become quantum critical when the electronic phase separation vanishes at
zero temperature into a quantum critical point. In this situation the critical
dynamical density fluctuations strongly affect the dynamics of the Cooper pair
fluctuations, which acquire a more singular character with a z=3 dynamical
critical index. This gives rise to a scenario that possibly rules the
disappearance of superconductivity when the electron density is reduced by
elecrostatic gating at the LaAlO3/SrTiO3 interface.Comment: 5 pages, 4 figure
Checkerboard and stripe inhomogeneities in cuprates
We systematically investigate charge-ordering phases by means of a restricted
and unrestricted Gutzwiller approximation to the single-band Hubbard model with
nearest () and next-nearest neighbor hopping (). When is small,
as appropriate for , stripes are found, whereas in
compounds with larger (such as and
) checkerboard structures are favored. In
contrast to the linear doping dependence found for stripes the charge
periodicity of checkerboard textures is locked to 4 unit cells over a wide
doping range. In addition we find that checkerboard structures are favored at
surfaces.Comment: 5 pages, 3 figure
Charge inhomogeneity coexisting with large Fermi surfaces
We discuss how stripes in cuprates can be compatible with a Fermi-liquid-like
Fermi surface and, at the same time, they give rise to a one-dimensional-like
pseudo Fermi surface in the momentum distribution function.Comment: Proceedings of the M2S conference, July 2006, Dresden; 2 pages, 1
figure to appear on Phisica
Fermi surface dichotomy on systems with fluctuating order
We investigate the effect of a dynamical collective mode coupled with
quasiparticles at specific wavevectors only. This coupling describes the
incipient tendency to order and produces shadow spectral features at high
energies, while leaving essentially untouched the low energy quasiparticles.
This allows to interpret seemingly contradictory experiments on underdoped
cuprates, where many converging evidences indicate the presence of charge
(stripe or checkerboard) order, which remains instead elusive in the Fermi
surface obtained from angle-resolved photoemission experiments.Comment: 11 pages, 10 figure
The Electron-Phonon Interaction in the Presence of Strong Correlations
We investigate the effect of strong electron-electron repulsion on the
electron-phonon interaction from a Fermi-liquid point of view: the strong
interaction is responsible for vertex corrections, which are strongly dependent
on the ratio. These corrections generically lead to a strong
suppression of the effective coupling between quasiparticles mediated by a
single phonon exchange in the limit. However, such effect
is not present when . Analyzing the Landau stability
criterion, we show that a sizable electron-phonon interaction can push the
system towards a phase-separation instability. A detailed analysis is then
carried out using a slave-boson approach for the infinite-U three-band Hubbard
model. In the presence of a coupling between the local hole density and a
dispersionless optical phonon, we explicitly confirm the strong dependence of
the hole-phonon coupling on the transferred momentum versus frequency ratio. We
also find that the exchange of phonons leads to an unstable phase with negative
compressibility already at small values of the bare hole-phonon coupling. Close
to the unstable region, we detect Cooper instabilities both in s- and d-wave
channels supporting a possible connection between phase separation and
superconductivity in strongly correlated systems.Comment: LateX 3.14, 04.11.1994 Preprint no.101
Phase separation from electron confinement at oxide interfaces
Oxide heterostructures are of great interest both for fundamental and
applicative reasons. In particular the two-dimensional electron gas at the
LaAlO/SrTiO or LaTiO/SrTiO interfaces displays many different
physical properties and functionalities. However there are clear indications
that the interface electronic state is strongly inhomogeneous and therefore it
is crucially relevant to investigate possible intrinsic electronic mechanisms
underlying this inhomogeneity. Here the electrostatic potential confining the
electron gas at the interface is calculated self-consistently, finding that the
electron confinement at the interface may induce phase separation, to avoid a
thermodynamically unstable state with a negative compressibility. This provides
a generic robust and intrinsic mechanism for the experimentally observed
inhomogeneous character of these interfaces.Comment: 8 pages and 4 figure
Kinks and waterfalls as signatures of competing order in angle-resolved photoemission spectra of La_{2-x}Sr_xCuO_4
We show that the so-called kinks and waterfalls observed in angle-resolved
photoemission spectra of La2-xSrxCuO4, a prototypical high-Tc superconducting
cuprate, result from the coupling of quasiparticles with two distinct nearly
critical collective modes with finite characteristic wave vectors, typical of
charge and spin fluctuations near a stripe instability. Both phonon-like charge
and spin collective modes are needed to account for the kinked quasiparticle
dispersions. This clarifies the long-standing question whether kinks are due to
phonons or spin waves and the nature of the bosonic mediators of the
electron-electron effective interaction in La2-xSrxCuO4.Comment: 5 pages, 4 figure
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