968 research outputs found
Comment on: Nonmonotonic Superconducting Order Parameter in NdCeCuO
In a recent letter Blumberg and collaborators claim that a non-monotonic
form for the superconducting order parameter is required to
explain their Raman scattering measurements in NdCeCuO . In
this comment we show with a simple model calculation that the basis for this
conclusion is insufficient. The proposed functional dependence of the gap is
neither consistent with their measured spectra nor compatible with other
experimental results. Therefore the issue of the superconduing gap in
electron-doped systems cannot be considered solved by now.Comment: Comment to the paper by Blumberg et al., Phys. Rev. Lett., 88, 107002
(2002
Raman scattering from a superconductivity-induced bound state in
It is shown that the sharp peak in the Raman spectrum of
superconducting is due to a bound state caused by the electron-phonon
coupling. Our theory explains why this peak appears only in the spectra with
symmetry and only in the but not bands. The properties
of the bound state and the Raman spectrum are investigated, also in the
presence of impurity scattering.Comment: 4 pages, 4 figures, will appear in PR
Nernst effect in the electron-doped cuprates
We calculate the normal state Nernst signal in the cuprates resulting from a
reconstruction of the Fermi surface due to spin density wave order. An order
parameter consistent with the reconstruction of the Fermi surface detected in
electron-doped materials is shown to sharply enhance the Nernst signal close to
optimal doping. Within a semiclassical treatment, the obtained magnitude and
position of the enhanced Nernst signal agrees with Nernst measurements in
electron-doped cuprates.Comment: 9 pages, 5 figures, revised version as accepted by Phys. Rev. B,
changed several citations and reference
Minimal energy cost of entanglement extraction
We compute the minimal energy cost for extracting entanglement from the
ground state of a bosonic or fermionic quadratic system. Specifically, we find
the minimal energy increase in the system resulting
from replacing an entangled pair of modes, sharing entanglement entropy , by a product state, and we show how to construct modes achieving this
minimal energy cost. Thus, we obtain a protocol independent lower bound on the
extraction of pure state entanglement from quadratic systems. Due to their
generality, our results apply to a large range of physical systems, as we
discuss with examples.Comment: 30+13 pages, 9 figure
Superconducting Gap and Pseudogap in Bi-2212
We present results of Raman scattering experiments in differently doped
Bi-2212 single crystals. Below Tc the spectra show pair-breaking features in
the whole doping range. The low frequency power laws confirm the existence of a
-wave order parameter. In the normal state between Tc and T* =
200K we find evidence for a pseudogap in B2g symmetry. Upon doping its effect
on the spectra decreases while its energy scale appears to be unchanged.Comment: 2 pages, 1 EPS figure; LT22 Proceedings to appear in Physica
Signatures of nematic quantum critical fluctuations in the Raman spectra of lightly doped cuprates
We consider the lightly doped cuprates YCaBaCuO
and LaSrCuO (with ,0.04), where the presence of a
fluctuating nematic state has often been proposed as a precursor of the stripe
(or, more generically, charge-density wave) phase, which sets in at higher
doping. We phenomenologically assume a quantum critical character for the
longitudinal and transverse nematic, and for the charge-ordering fluctuations,
and investigate the effects of these fluctuations in Raman spectra. We find
that the longitudinal nematic fluctuations peaked at zero transferred momentum
account well for the anomalous Raman absorption observed in these systems in
the channel, while the absence of such effect in the channel
may be due to the overall suppression of Raman response at low frequencies,
associated with the pseudogap. While in YCaBaCuO the
low-frequency lineshape is fully accounted by longitudinal nematic collective
modes alone, in LaSrCuO also charge-ordering modes with finite
characteristic wavevector are needed to reproduce the shoulders observed in the
Raman response. This different involvement of the nearly critical modes in the
two materials suggests a different evolution of the nematic state at very low
doping into the nearly charge-ordered state at higher doping.Comment: 12 pages with 10 figures, to appear in Phys. Rev. B 201
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