1,055 research outputs found
Shadow features and shadow bands in the paramagnetic state of cuprate superconductors
The conditions for the precursors of antiferromagnetic bands in cuprate
superconductors are studied using weak-to-intermediate coupling approach. It is
shown that there are, in fact, three different precursor effects due to the
proximity to antiferromagnetic instability: i) the shadow band which associated
with new pole in the Green's function ii) the dispersive shadow feature due to
the thermal enhancement of the scattering rate and iii) the non-dispersive
shadow feature due to quantum spin fluctuation that exist only in
scan of the spectral function . I found
that dispersive shadow peaks in can exist at finite
temperature T in the renormalized classical regime, when ,
( is the characteristic energy of
spin fluctuations, is the thermal wave length of electron). In
contrast at zero temperature, only non-dispersive shadow feature in has been found. I found, however, that the latter
effect is always very small. The theory predict no shadow effects in the
optimally doped materials. The conditions for which shadow peaks can be
observed in photoemission are discussed.Comment: 6 pages, REVTEX, 2 ps figures, version to be published in PR
Collective Spin Fluctuation Mode and Raman Scattering in Superconducting Cuprates
Although the low frequency electronic Raman response in the superconducting
state of the cuprates can be largely understood in terms of a d-wave energy
gap, a long standing problem has been an explanation for the spectra observed
in the polarization orientations. We present calculations which
suggest that the peak position of the observed spectra is due to a
collective spin fluctuation mode.Comment: 4 pages, 5 eps figure
Exact Bond Ordered Ground State for the Transition Between the Band and the Mott Insulator
We derive an effective Hamiltonian for an ionic Hubbard chain,
valid for , where is the hopping, the Coulomb
repulsion, and the charge transfer energy. is the minimal
model for describing the transition from the band insulator (BI) () and the Mott insulator (MI) (). Using spin-particle
transformations (Phys. Rev. Lett. \textbf{86}, 1082 (2001)), we map
into an SU(3) antiferromagnetic Heisenberg model whose
exact ground state is known. In this way, we show rigorously that a
spontaneously dimerized insulating ferroelectric phase appears in the
transition region between the BI and MI
Stripe orientation in an anisotropic t-J model
The tilt pattern of the CuO_6 octahedra in the LTT phase of the cuprate
superconductors leads to planar anisotropies for the exchange coupling and
hopping integrals. Here, we show that these anisotropies provide a possible
structural mechanism for the orientation of stripes. A t_x-t_y-J_x-J_y model
thus serves as an effective Hamiltonian to describe stripe formation and
orientation in LTT-phase cuprates.Comment: 3 pages, 3 figure
Ground-state van der Waals forces in planar multilayer magnetodielectrics
Within the frame of lowest-order perturbation theory, the van der Waals
potential of a ground-state atom placed within an arbitrary dispersing and
absorbing magnetodielectric multilayer system is given. Examples of an atom
situated in front of a magnetodielectric plate or between two such plates are
studied in detail. Special emphasis is placed on the competing attractive and
repulsive force components associated with the electric and magnetic matter
properties, respectively, and conditions for the formation of repulsive
potential walls are given. Both numerical and analytical results are presented.Comment: 16 pages, 8 figures, minor correction
On different lagrangian formalisms for vector resonances within chiral perturbation theory
We study the relation of vector Proca field formalism and antisymmetric
tensor field formalism for spin-one resonances in the context of the large N_C
inspired chiral resonance Lagrangian systematically up to the order O(p6) and
give a transparent prescription for the transition from vector to antisymmetric
tensor Lagrangian and vice versa. We also discuss the possibility to describe
the spin-one resonances using an alternative "mixed" first order formalism,
which includes both types of fields simultaneously, and compare this one with
the former two. We also briefly comment on the compatibility of the above
lagrangian formalisms with the high-energy constraints for concrete VVP
correlator.Comment: 34 pages, 3 figure
Phase diagram of the two-dimensional t--J model at low doping
The phase diagram of the planar t--J model at small hole doping is
investigated by finite size scaling of exact diagonalisation data of NXN
clusters (up to 26). Hole-droplet binding energies, compressibility and static
spin and charge correlations are calculated. Short range antiferromagnetic
correlations can produce attractive forces between holes leading to a very rich
phase diagram including a liquid of d-wave hole pairs (for ), a
liquid of hole droplets (quartets) for larger J/t ratios ()
and, at even larger coupling J/t, an instability towards phase separation.Comment: 3 pages, latex, 5 postscript figures, uuencode
Can Short-Range Interactions Mediate a Bose Metal Phase in 2D?
We show here based on a 1-loop scaling analysis that short-range interactions
are strongly irrelevant perturbations near the insulator-superconductor (IST)
quantum critical point. The lack of any proof that short-range interactions
mediate physics which is present only in strong coupling leads us to conclude
that short-range interactions are strictly irrelevant near the IST quantum
critical point. Hence, we argue that no new physics, such as the formation of a
uniform Bose metal phase can arise from an interplay between on-site and
nearest-neighbour interactions.Comment: 3 pages, 1 .eps file. SUbmitted to Phys. Rev.
A Consistent Picture of Electronic Raman Scattering and Infrared Conductivity in the Cuprates
Calculations are presented for electronic Raman scattering and infrared
conductivity in a superconductor including the effects of
elastic scattering via anisotropic impurities and inelastic spin-fluctuation
scattering. A consistent description of experiments on optimally doped Bi-2212
is made possible by considering the effects of correlations on both inelastic
and elastic scattering.Comment: 4 pages Revtex, 5 embedded eps file
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