1,070 research outputs found

### Experimental Evidence for Topological Doping in the Cuprates

Some recent experiments that provide support for the concept of topological
doping in cuprate superconductors are discussed. Consistent with the idea of
charge segregation, it is argued that the scattering associated with the
``resonance'' peak found in YBa(2)Cu(3)O(6+x) and Bi(2)Sr(2)CaCu(2)O(8+\delta)
comes from the Cu spins and not from the doped holes.Comment: 5 pp., uses aipproc.sty, for Proc. of U. Miami Conf: HTS9

### Charge stripes in cuprate superconductors: The middle way

Charge and spin stripe order is a type of electronic crystal observed in
certain layered cuprates associated with high-temperature superconductivity.
Quantum-disordered stripes could be relevant for understanding the
superconductivity. Here I discuss recent experimental characterizations of the
stripe-ordered state in La(1.875)Ba(0.125)CuO(4), and compare them with
properties of superconducting compositions.Comment: 6 pp., submitted to the proceedings of ECRYS 2005, J. Phys. I

### Stripes and superconductivity in cuprate superconductors

One type of order that has been observed to compete with superconductivity in
cuprates involves alternating charge and antiferromagnetic stripes. Recent
neutron scattering studies indicate that the magnetic excitation spectrum of a
stripe-ordered sample is very similar to that observed in superconducting
samples. In fact, it now appears that there may be a universal magnetic
spectrum for the cuprates. One likely implication of this universal spectrum is
that stripes of a dynamic form are present in the superconducting samples. On
cooling through the superconducting transition temperature, a gap opens in the
magnetic spectrum, and the weight lost at low energy piles up above the gap;
the transition temperature is correlated with the size of the spin gap.
Depending on the magnitude of the spin gap with respect to the magnetic
spectrum, the enhanced magnetic scattering at low temperature can be either
commensurate or incommensurate. Connections between stripe correlations and
superconductivity are discussed.Comment: 6 pp, for proceedings of SPIE mtg., July 31-Aug. 4, 2005 in San Dieg

### Charge stripes and spin correlations in copper-oxide superconductors

Recent neutron diffraction studies have yielded evidence that, in a
particular cuprate family, holes doped into the CuO(2) planes segregate into
stripes that separate antiferromagnetic domains. Here it is shown that such a
picture provides a quantitatively consistent interpretation of the spin
fluctuations measured by neutron scattering in La(1.85)Sr(0.15)CuO(4) and
YBa(2)Cu(3)O(6+x).Comment: 4 pp., LaTeX, uses espcrc2.sty, 2 eps figures included with psfig,
for proceedings of M2S-HTSC-

### Spin Dynamics in an Ordered Stripe Phase

Inelastic neutron scattering has been used to measure the low-energy spin
excitations in the ordered charge-stripe phase of La(2)NiO(4+d) with d=0.133.
Spin-wave-like excitations disperse away from the incommensurate magnetic
superlattice points with a velocity ~60% of that in the d=0 compound.
Incommensurate inelastic peaks remain well-resolved up to at least twice the
magnetic ordering temperature. Paramagnetic scattering from a d=0.105 sample,
which has a N\'eel-ordered ground state, shows anomalies suggestive of
incipient stripe correlations. Similarities between these results and
measurements on superconducting cuprates are discussed.Comment: 5 pp, 2 col., REVTeX, 4 epsf figures embedded with psfig; Abstract
and introduction have been revise

### Incompatibility of modulated checkerboard patterns with the neutron scattering resonance peak in cuprate superconductors

Checkerboard patterns have been proposed in order to explain STM experiments
on the cuprates BSCCO and Na-CCOC. However the presence of these patterns has
not been confirmed by a bulk probe such as neutron scattering. In particular,
simple checkerboard patterns are inconsistent with neutron scattering data, in
that they have low energy incommsensurate (IC) spin peaks rotated 45 degrees
from the direction of the charge IC peaks. However, it is unclear whether other
checkerboard patterns can solve the problem. In this paper, we have studied
more complicated checkerboard patterns ("modulated checkerboards") by using
spin wave theory and analyzed noncollinear checkerboards as well. We find that
the high energy response of the modulated checkerboards is inconsistent with
neutron scattering results, since they fail to exhibit a resonance peak at
(pi,pi), which has recently been shown to be a universal feature of cuprate
superconductors. We further argue that the newly proposed noncollinear
checkerboard also lacks a resonance peak. We thus conclude that to date no
checkerboard pattern has been proposed which satisfies both the low energy
constraints and the high energy constraints imposed by the current body of
experimental data in cuprate superconductors.Comment: 5 pages, 5 figures, Fig.2 update

### Stripe orders in the extended Hubbard model

We study stripe orders of charge and spin density waves in the extended
Hubbard model with the nearest-neighbor Coulomb repulsion V within the mean
field approximation. We obtain V vs. T(temperature) phase diagram for the
on-site Coulomb interaction U/t=8.0 and the filling n=0.8, here t is a
nearest-neighbor transfer energy. Our result shows that the diagonal stripe
spin density wave state (SDW) is stable for small V, but for large V the most
stable state changes to a charge density wave-antiferromagnetic (CDW-AF) state.
Especially we find at low temperature and for a certain range of value of V, a
vertical stripe CDW-AF state becomes stable.Comment: LaTeX 9 pages, 17 figures, uses jpsj.st

### Energetics of Domain Walls in the 2D t-J model

Using the density matrix renormalization group, we calculate the energy of a
domain wall in the 2D t-J model as a function of the linear hole density
\rho_\ell, as well as the interaction energy between walls, for J/t=0.35. Based
on these results, we conclude that the ground state always has domain walls for
dopings 0 < x < 0.3. For x < 0.125, the system has (1,0) domain walls with
\rho_\ell ~ 0.5, while for 0.125 < x < 0.17, the system has a possibly
phase-separated mixture of walls with \rho_\ell ~ 0.5 and \rho_\ell =1. For x >
0.17, there are only walls with \rho_\ell =1. For \rho_\ell = 1, diagonal (1,1)
domain walls have very nearly the same energy as (1,0) domain walls.Comment: Several minor changes. Four pages, four encapsulated figure

### Incommensurability and spin excitations of diagonal stripes in cuprates

Based on the time-dependent Gutzwiller approximation we study the possibility
that the diagonal incommensurate spin scattering in strongly underdoped
lanthanum cuprates originates from antiferromagnetic domain walls (stripes).
Calculation of the dynamic spin response for stripes in the diagonal phase
yields the characteristic hour glass dispersion with the crossing of low energy
Goldstone and high-energy branches at a characteristic energy Ecross at the
antiferromagnetic wave-vector Q_{AF}. The high energy part is close to the
parent antiferromagnet. Our results suggest that inelastic neutron scattering
experiments on strongly underdoped lanthanum cuprates can be understood as due
to a mixture of bond centered and site centered stripe configurations with
substantial disorder.Comment: 4 pages, 5 figure

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