692 research outputs found
Flux Phase as a Dynamic Jahn-Teller Phase: Berryonic Matter in the Cuprates?
There is considerable evidence for some form of charge ordering on the
hole-doped stripes in the cuprates, mainly associated with the low-temperature
tetragonal phase, but with some evidence for either charge density waves or a
flux phase, which is a form of dynamic charge-density wave. These three states
form a pseudospin triplet, demonstrating a close connection with the E X e
dynamic Jahn-Teller effect, suggesting that the cuprates constitute a form of
Berryonic matter. This in turn suggests a new model for the dynamic Jahn-Teller
effect as a form of flux phase. A simple model of the Cu-O bond stretching
phonons allows an estimate of electron-phonon coupling for these modes,
explaining why the half breathing mode softens so much more than the full
oxygen breathing mode. The anomalous properties of provide a coupling
(correlated hopping) which acts to stabilize density wave phases.Comment: Major Revisions: includes comparisons with specific cuprate phonon
modes, 16 eps figures, revte
Antiferromagnetic and van Hove Scenarios for the Cuprates: Taking the Best of Both Worlds
A theory for the high temperature superconductors is proposed. Holes are
spin-1/2, charge e, quasiparticles strongly dressed by spin fluctuations. Based
on their dispersion, it is claimed that the experimentally observed van Hove
singularities of the cuprates are likely originated by antiferromagnetic (AF)
correlations. From the two carriers problem in the 2D t-J model, an effective
Hamiltonian for holes is defined with %no free parameters. This effective model
has superconductivity in the channel, a critical
temperature at the optimal hole density, ,
and a quasiparticle lifetime linearly dependent with energy. Other experimental
results are also reproduced by the theory.Comment: 12 pages, 4 figures (on request), RevTeX (version 3.0), preprint
NHMF
Van Hove Exciton-Cageons and High-T Superconductivity: VIIID Solitons and Nonlinear Dynamics
The low-temperature orthorhombic (LTO) phase transition in
LaSrCuO can be interpreted as a dynamic Jahn-Teller effect, in
which the degenerate electronic states are associated with the large densities
of states at the two van Hove singularities. The equations describing this
phase are strongly nonlinear. This paper illustrates some consequences of the
nonlinearity, by presenting a rich variety of exact nonlinear wave solutions
for the model.
Of particular interest are soliton lattice solutions: arrays of domain walls
separating regions of local low-temperature tetragonal (LTT) symmetry. These
arrays have a {\it macroscopic} average symmetry higher than LTT. These
lattices can display either orthorhombic (`orthons') or tetragonal (`tetrons')
symmetry, and can serve as models for a microscopic description of the dynamic
JT LTO and high-temperature tetragonal phases, respectively.Comment: 17 pages plain TeX, 14 figures available upon reques
Mild malformations of cortical development in sleep-related hypermotor epilepsy due to KCNT1 mutations
open14siMutations in the sodium-activated potassium channel gene KCNT1 have been associated with nonlesional sleep-related hypermotor epilepsy (SHE). We report the co-occurrence of mild malformation of cortical development (mMCD) and KCNT1 mutations in four patients with SHE. Focal cortical dysplasia type I was neuropathologically diagnosed after epilepsy surgery in three unrelated MRI-negative patients, periventricular nodular heterotopia was detected in one patient by MRI. Our findings suggest that KCNT1 epileptogenicity may result not only from dysregulated excitability by controlling Na+K+ transport, but also from mMCD. Therefore, pathogenic variants in KCNT1 may encompass both lesional and nonlesional epilepsies.openRubboli G.; Plazzi G.; Picard F.; Nobili L.; Hirsch E.; Chelly J.; Prayson R.A.; Boutonnat J.; Bramerio M.; Kahane P.; Dibbens L.M.; Gardella E.; Baulac S.; Moller R.S.Rubboli, G.; Plazzi, G.; Picard, F.; Nobili, L.; Hirsch, E.; Chelly, J.; Prayson, R. A.; Boutonnat, J.; Bramerio, M.; Kahane, P.; Dibbens, L. M.; Gardella, E.; Baulac, S.; Moller, R. S
Electron Dynamics in NdCeCuO: Evidence for the Pseudogap State and Unconventional c-axis Response
Infrared reflectance measurements were made with light polarized along the a-
and c-axis of both superconducting and antiferromagnetic phases of electron
doped NdCeCuO. The results are compared to
characteristic features of the electromagnetic response in hole doped cuprates.
Within the CuO planes the frequency dependent scattering rate,
1/, is depressed below 650 cm; this behavior is a
hallmark of the pseudogap state. While in several hole doped compounds the
energy scales associated with the pseudogap and superconducting states are
quite close, we are able to show that in NdCeCuO
the two scales differ by more than one order of magnitude. Another feature of
the in-plane charge response is a peak in the real part of the conductivity,
, at 50-110 cm which is in sharp contrast with the
Drude-like response where is centered at . This
latter effect is similar to what is found in disordered hole doped cuprates and
is discussed in the context of carrier localization. Examination of the c-axis
conductivity gives evidence for an anomalously broad frequency range from which
the interlayer superfluid is accumulated. Compelling evidence for the pseudogap
state as well as other characteristics of the charge dynamics in
NdCeCuO signal global similarities of the cuprate
phase diagram with respect to electron and hole doping.Comment: Submitted to PR
Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive Pi0 production at midrapidity in
polarized proton collisions at sqrt(s) = 200 GeV. The cross section was
measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be
in good agreement with a next-to-leading order perturbative QCD calculation.
The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T <
11 GeV/c and excludes a maximal positive gluon polarization in the proton. The
mean transverse momentum fraction of Pi0's in their parent jets was found to be
around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC
Partonic flow and -meson production in Au+Au collisions at = 200 GeV
We present first measurements of the -meson elliptic flow
() and high statistics distributions for different
centralities from = 200 GeV Au+Au collisions at RHIC. In
minimum bias collisions the of the meson is consistent with the
trend observed for mesons. The ratio of the yields of the to those of
the as a function of transverse momentum is consistent with a model
based on the recombination of thermal quarks up to GeV/,
but disagrees at higher momenta. The nuclear modification factor () of
follows the trend observed in the mesons rather than in
baryons, supporting baryon-meson scaling. Since -mesons are
made via coalescence of seemingly thermalized quarks in central Au+Au
collisions, the observations imply hot and dense matter with partonic
collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR
Measurement of Transverse Single-Spin Asymmetries for Di-Jet Production in Proton-Proton Collisions at GeV
We report the first measurement of the opening angle distribution between
pairs of jets produced in high-energy collisions of transversely polarized
protons. The measurement probes (Sivers) correlations between the transverse
spin orientation of a proton and the transverse momentum directions of its
partons. With both beams polarized, the wide pseudorapidity () coverage for jets permits separation of Sivers functions for the valence
and sea regions. The resulting asymmetries are all consistent with zero and
considerably smaller than Sivers effects observed in semi-inclusive deep
inelastic scattering (SIDIS). We discuss theoretical attempts to reconcile the
new results with the sizable transverse spin effects seen in SIDIS and forward
hadron production in pp collisions.Comment: 6 pages total, 1 Latex file, 3 PS files with figure
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