2,339 research outputs found
Reconstructing the bulk Fermi surface and the superconducting gap properties from Neutron Scattering experiments
We develop an analytical tool to extract bulk electronic properties of
unconventional superconductors through inelastic neutron scattering (INS)
spectra. Since the spin excitation spectrum in the superconducting (SC) state
originates from Bogoliubov quasiparticle scattering associated with Fermi
surface nesting, its energy-momentum relation--the so called `hour-glass'
feature--can be inverted to reveal the Fermi momentum dispersion of the
single-particle spectrum as well as the corresponding SC gap function. The
inversion procedure is analogous to the quasiparticle interference (QPI) effect
in scanning tunneling microscopy (STM). Whereas angle-resolved photoemission
spectroscopy (ARPES) and STM provide surface sensitive information, our
inversion procedure provides bulk electronic properties. The technique is
essentially model independent and can be applied to a wide variety of
materials.Comment: 8 pages, 4 figure
Nonmonotonic superconducting gap in electron-doped PrLaCeCuO: Evidence of coexisting antiferromagnetism and superconductivity?
Recent experiments on PrLaCeCuO observe an anisotropic
spin-correlation gap and a nonmonotonic superconducting (SC) gap, which we
analyze within the framework of a
model with a
pairing interaction including a third harmonic contribution. By
introducing a realistic broadening of the quasiparticle spectrum to reflect
small-angle scattering, our computations explain the experimental observations,
especially the presence of a maximum in the leading edge gap in the vicinity of
the hot-spots. Our analysis suggests that the material behaves like a {\it
two-band} superconductor with the d-wave third harmonic acting as the {\it
interband pairing gap}, and that the anti-ferromagnetic (AFM) and SC orders
co-exist in a uniform phase
Failure of t-J models in describing doping evolution of spectral weight in x-ray scattering, optical and photoemission spectra of the cuprates
We have analyzed experimental evidence for an anomalous transfer of spectral
weight from high to low energy scales in both electron and hole doped cuprates
as a function of doping. X-ray scattering, optical and photoemission spectra
are all found to show that the high energy spectral weight decreases with
increasing doping at a rate much faster than predictions of the large limit
calculations. The observed doping evolution is however well-described by an
intermediate coupling scenario where the effective Hubbard is comparable to
the bandwidth. The experimental spectra across various spectroscopies are
inconsistent with fixed- exact diagonalization or quantum Monte Carlo
calculations, and suggest a significant doping dependence of the effective
in the cuprates.Comment: Accepted for Phys. Rev. B (2010). 7 pages, 4 figure
Visualizing electron pockets in cuprate superconductors
Fingerprint of the electron-pocket in cuprates has been obtained only in
numerous magneto-transport measurements, but its absence in spectroscopic
observations pose a long-standing mystery. We develop a theoretical tool to
provide ways to detect electron-pockets via numerous spectroscopies including
scanning tunneling microscopy (STM) spectra, inelastic neutron scattering
(INS), and angle-resolved photoemission spectroscopy (ARPES). We show that the
quasiparticle-interference (QPI) pattern, measured by STM, shows additional 7
vectors associated with the scattering on the electron-pocket, than
that on the hole-pocket. Furthermore, the Bogolyubov quasiparticle scatterings
of the electron pocket may lead to a second magnetic resonance mode in the INS
spectra at a higher resonance energy. Finally, we reanalyze some STM, INS, and
ARPES experimental data of several cuprate compounds which dictates the direct
fingerprints of electron pockets in these systems.Comment: 10 pages, 6 figures, submitte
Remnant Fermi Surfaces in Photoemission
Recent experiments have introduced a new concept for analyzing the
photoemission spectra of correlated electrons -- the remnant Fermi surface
(rFs), which can be measured even in systems which lack a conventional Fermi
surface. Here, we analyze the rFs in a number of interacting electron models,
and find that the results fall into two classes. For systems with pairing
instabilities, the rFs is an accurate replica of the true Fermi surface. In the
presence of nesting instabilities, the rFs is a map of the resulting
superlattice Brillouin zone. The results suggest that the gap in Ca_2CuO_2Cl_2
is of nesting origin.Comment: 4 pages LaTex, 3 ps figure
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