953 research outputs found
Universal zero-frequency Raman slope in a d-wave superconductor
It is known that for an unconventional superconductor with nodes in the gap,
the in-plane microwave or dc conductivity saturates at low temperatures to a
universal value independent of the impurity concentration. We demonstrate that
a similar feature can be accessed using channel-dependent Raman scattering. It
is found that, for a -wave superconductor, the slope of
low-temperature Raman intensity at zero frequency is universal in the
and channels, but not in the channel. Moreover, as opposed to
the microwave conductivity, universal Raman slopes are sensitive not only to
the existence of a node, but also to different pairing states and should allow
one to distinguish between such pairing states.Comment: 5 page
Symmetry dependence of phonon lineshapes in superconductors with anisotropic gaps
The temperature dependence below of the lineshape of optical phonons
of different symmetry as seen in Raman scattering is investigated for
superconductors with anisotropic energy gaps. It is shown that the symmetry of
the electron-phonon vertex produces non-trivial couplings to an anisotropic
energy gap which leads to unique changes in the phonon lineshape for phonons of
different symmetry. The phonon lineshape is calculated in detail for
and phonons in a superconductor with pairing
symmetry. The role of satellite peaks generated by the electron-phonon coupling
are also addressed. The theory accounts for the substantial phonon narrowing of
the phonon, while narrowing of the phonon which is
indistinguishable from the normal state is shown, in agreement with recent
measurements on BSCCO.Comment: 15 pages (3 Figures available upon request), Revtex, 1
Momentum dependent light scattering in insulating cuprates
We investigate the problem of inelastic x-ray scattering in the spin
Heisenberg model on the square lattice. We first derive a momentum dependent
scattering operator for the and polarization geometries. On
the basis of a spin-wave analysis, including magnon-magnon interactions and
exact-diagonalizations, we determine the qualitative shape of the spectra. We
argue that our results may be relevant to help interpret inelastic x-ray
scattering experiments in the antiferromagnetic phase of the cuprates.Comment: 5 pages, 3 figures, to appear in PR
Time-resolved photoemission of correlated electrons driven out of equilibrium
We describe the temporal evolution of the time-resolved photoemission
response of the spinless Falicov-Kimball model driven out of equilibrium by
strong applied fields. The model is one of the few possessing a metal-insulator
transition and admitting an exact solution in the time domain. The
nonequilibrium dynamics, evaluated using an extension of dynamical mean-field
theory, show how the driven system differs from two common viewpoints - a
quasiequilibrium system at an elevated effective temperature (the "hot"
electron model) or a rapid interaction quench ("melting" of the Mott gap) - due
to the rearrangement of electronic states and redistribution of spectral
weight. The results demonstrate the inherent trade-off between energy and time
resolution accompanying the finite width probe pulses, characteristic of those
employed in pump-probe time-domain experiments, which can be used to focus
attention on different aspects of the dynamics near the transition.Comment: Original: 5 pages, 3 figures; Replaced: updated text and figures, 5
pages, 4 figure
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