816 research outputs found
Pseudogap, charge order, and pairing density wave at the hot spots in cuprate superconductors
We address the timely issue of the presence of charge ordering at the
hot-spots in the pseudo-gap phase of cuprate superconductors in the context of
an emergent SU(2)-symmetry which relates the charge and pairing sectors.
Performing the Hubbard-Stratonovich decoupling such that the free energy stays
always real and physically meaningful we exhibit three solutions of the
spin-fermion model at the hot spots. A careful examination of their stability
and free energy shows that, at low temperature, the system tends towards a
co-existence of charge density wave (CDW) and the composite order parameter
made of diagonal quadrupolar density wave and pairing fluctuations of Ref.
[Nat. Phys. , 1745 (2013)].The CDW is sensitive to the shape of the
Fermi surface in contrast to the diagonal quadrupolar order, which is immune to
it. SU(2) symmetry within the pseudo-gap phase also applies to the CDW state,
which therefore admits a pairing density pave counterpart breaking time
reversal symmetry.Comment: 15 pages, 15 figures, final version + typo corrected in Eq. (12
Charge orders, magnetism and pairings in the cuprate superconductors
We review the recent developments in the field of cuprate superconductors
with the special focus on the recently observed charge order in the underdoped
compounds. We introduce new theoretical developments following the study of the
antiferromagnetic (AF) quantum critical point (QCP) in two dimensions, in which
preemptive orders in the charge and superconducting (SC) sectors emerged, that
are in turn related by an SU(2) symmetry. We consider the implications of this
proliferation of orders in the underdoped region, and provide a study of the
type of fluctuations which characterize the SU(2) symmetry. We identify an
intermediate energy scale where the SU(2) pairing fluctuations are dominant and
argue that they are unstable towards the formation of a Resonant Peierls
Excitonic (RPE) state at the pseudogap (PG) temperature . We discuss the
implications of this scenario for a few key experiments.Comment: 16 pages, 17 figure
The nature of iron-oxygen vacancy defect centers in PbTiO3
The iron(III) center in ferroelectric PbTiO3 together with an oxygen vacancy
forms a charged defect associate, oriented along the crystallographic c-axis.
Its microscopic structure has been analyzed in detail comparing results from a
semi-empirical Newman superposition model analysis based on finestructure data
and from calculations using density functional theory.
Both methods give evidence for a substitution of Fe3+ for Ti4+ as an acceptor
center. The position of the iron ion in the ferroelectric phase is found to be
similar to the B-site in the paraelectric phase. Partial charge compensation is
locally provided by a directly coordinated oxygen vacancy.
Using high-resolution synchrotron powder diffraction, it was verified that
lead titanate remains tetragonal down to 12 K, exhibiting a c/a-ratio of
1.0721.Comment: 11 pages, 5 figures, accepted in Phys. Rev.
Keratinocytes at the uppermost layer of epidermis might act as sensors of atmospheric pressure change
Measurement of azimuthal asymmetries in inclusive charged dipion production in annihilations at = 3.65 GeV
We present a measurement of the azimuthal asymmetries of two charged pions in
the inclusive process based on a data set of 62
at the center-of-mass energy GeV collected with
the BESIII detector. These asymmetries can be attributed to the Collins
fragmentation function. We observe a nonzero asymmetry, which increases with
increasing pion momentum. As our energy scale is close to that of the existing
semi-inclusive deep inelastic scattering experimental data, the measured
asymmetries are important inputs for the global analysis of extracting the
quark transversity distribution inside the nucleon and are valuable to explore
the energy evolution of the spin-dependent fragmentation function.Comment: 7 pages, 5 figure
Measurement of the Cross Section between 600 and 900 MeV Using Initial State Radiation
We extract the cross section in the energy
range between 600 and 900 MeV, exploiting the method of initial state
radiation. A data set with an integrated luminosity of 2.93 fb taken at
a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII
collider is used. The cross section is measured with a systematic uncertainty
of 0.9%. We extract the pion form factor as well as the
contribution of the measured cross section to the leading order hadronic vacuum
polarization contribution to . We find this value to be
.Comment: 14 pages, 7 figures, accepted by PL
Study of
We present an analysis of the decay based
on data collected by the BESIII experiment at the resonance. Using
a nearly background-free sample of 18262 events, we measure the branching
fraction . For GeV/ the partial branching fraction is
. A partial wave analysis shows that the dominant
component is accompanied by an \emph{S}-wave contribution accounting for
of the total rate and that other components are
negligible. The parameters of the resonance and of the
form factors based on the spectroscopic pole dominance predictions are also
measured. We also present a measurement of the helicity
basis form factors in a model-independent way.Comment: 17 pages, 6 figure
Measurements of absolute hadronic branching fractions of baryon
Using of collisions recorded at
with the BESIII detector, we report first measurements
of absolute hadronic branching fractions of Cabibbo-favored decays of the
baryon with a double-tag technique. A global least-square
fitter is utilized to improve the measured precision. Among the measurements
for twelve decay modes, the branching fraction for
is determined to be
, where the first uncertainty is statistical and the
second is systematic. In addition, the measurements of the branching fractions
of the other eleven Cabbibo-favored hadronic decay modes are significantly
improved
- …