380 research outputs found
Direct observation of particle-hole mixing in the superconducting state by angle-resolved photoemission
Particle-hole (p-h) mixing is a fundamental consequence of the existence of a
pair condensate. We present direct experimental evidence for p-h mixing in the
angle-resolved photoemission (ARPES) spectra in the superconducting state of
Bi_2Sr_2CaCu_2O_{8+\delta}. In addition to its pedagogical importance, this
establishes unambiguously that the gap observed in ARPES is associated with
superconductivity.Comment: 3 pages, revtex, 4 postscript figure
S and D Wave Mixing in High Superconductors
For a tight binding model with nearest neighbour attraction and a small
orthorhombic distortion, we find a phase diagram for the gap at zero
temperature which includes three distinct regions as a function of filling. In
the first, the gap is a mixture of mainly -wave with a smaller extended
-wave part. This is followed by a region in which there is a rapid increase
in the -wave part accompanied by a rapid increase in relative phase between
and from 0 to . Finally, there is a region of dominant with a
mixture of and zero phase. In the mixed region with a finite phase, the
-wave part of the gap can show a sudden increase with decreasing temperature
accompanied with a rapid increase in phase which shows many of the
characteristics measured in the angular resolved photoemission experiments of
Ma {\em et al.} in Comment: 12 pages, RevTeX 3.0, 3 PostScript figures uuencoded and compresse
Superconducting gap in the presence of bilayer splitting in underdoped Bi(Pb)2212
The clearly resolved bilayer splitting in ARPES spectra of the underdoped
Pb-Bi2212 compound rises the question of how the bonding and antibonding sheets
of the Fermi surface are gapped in the superconducting state. Here we compare
the superconducting gaps for both split components and show that within the
experimental uncertainties they are identical. By tuning the relative intensity
of the bonding and antibonding bands using different excitation conditions we
determine the precise {\bf k}-dependence of the leading edge gap. Significant
deviations from the simple cos()-cos() gap function for the
studied doping level are detected.Comment: 5 pages, 4 figures (revtex4
Evolution of the pairing pseudogap in the spectral function with interplane anisotropy
We study the pairing pseudogap in the spectral function as a function of
interplane coupling. The analytical expressions for the self-energy in the
critical regime are obtained for any degree of anisotropy. The frequency
dependence of the self-energy is found to be qualitatively different in two and
three dimensions, and the crossover from two to three dimensional behavior is
discussed. In particular, by considering the anisotropy of the Fermi velocity
and gap along the Fermi surface, we can qualitatively explain recent
photoemission experiments on high temperature superconductors concerning the
temperature dependent Fermi arcs seen in the pseudogap phase.Comment: 20 pages, revtex, 5 encapsulated postscript figures include
On the determination of the Fermi surface in high-Tc superconductors by angle-resolved photoemission spectroscopy
We study the normal state electronic excitations probed by angle resolved
photoemission spectroscopy (ARPES) in Bi2201 and Bi2212. Our main goal is to
establish explicit criteria for determining the Fermi surface from ARPES data
on strongly interacting systems where sharply defined quasiparticles do not
exist and the dispersion is very weak in parts of the Brillouin zone.
Additional complications arise from strong matrix element variations within the
zone. We present detailed results as a function of incident photon energy, and
show simple experimental tests to distinguish between an intensity drop due to
matrix element effects and spectral weight loss due to a Fermi crossing. We
reiterate the use of polarization selection rules in disentangling the effect
of umklapps due to the BiO superlattice in Bi2212. We conclude that, despite
all the complications, the Fermi surface can be determined unambiguously: it is
a single large hole barrel centered about (pi,pi) in both materials.Comment: Expanded discussion of symmetrization method in Section 5, figures
remain the sam
Using dynamic, full cache locking and genetic algorithms for cache size minimization in multitasking, preemptive, real-time systems
The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-45008-2_13Cache locking have shown during the last years their usefulness easing the schedulability analysis of multitasking, preemptive, real-time systems. Cache locking provides a high degree of predictability while system performance is maintained at a similar level to that provided by regular, highly unpredictable, non-locked cache. Cache locking may also be useful to reduce hardware costs by means of reducing the size of the cache memory needed to make a real-time system schedulable.This work shows how full, dynamic cache locking may help to reduce the size of the cache memory versus a regular cache. This reduction is possible thanks to a genetic algorithm that selects the set of instructions that have to be locked in cache to provide the maximum cache size minimization while keeping the system schedulable.This work is partially supported by PAID-06-11/2055 of Universitat Politècnica de València and TIN2011-28435-C03-01 of Ministerio de Ciencia e InnovaciĂłn.MartĂ Campoy, A.; RodrĂguez Ballester, F.; Ors Carot, R. (2013). Using dynamic, full cache locking and genetic algorithms for cache size minimization in multitasking, preemptive, real-time systems. En Theory and Practice of Natural Computing. Springer Verlag (Germany). 157-168. https://doi.org/10.1007/978-3-642-45008-2S15716
CTCF genetic alterations in endometrial carcinoma are pro-tumorigenic
CTCF is a haploinsufficient tumour suppressor gene with diverse normal functions in genome structure and gene regulation. However the mechanism by which CTCF haploinsufficiency contributes to cancer development is not well understood. CTCF is frequently mutated in endometrial cancer. Here we show that most CTCF mutations effectively result in CTCF haploinsufficiency through nonsense-mediated decay of mutant transcripts, or loss-of-function missense mutation. Conversely, we identified a recurrent CTCF mutation K365T, which alters a DNA binding residue, and acts as a gain-of-function mutation enhancing cell survival. CTCF genetic deletion occurs predominantly in poor prognosis serous subtype tumours, and this genetic deletion is associated with poor overall survival. In addition, we have shown that CTCF haploinsufficiency also occurs in poor prognosis endometrial clear cell carcinomas and has some association with endometrial cancer relapse and metastasis. Using shRNA targeting CTCF to recapitulate CTCF haploinsufficiency, we have identified a novel role for CTCF in the regulation of cellular polarity of endometrial glandular epithelium. Overall, we have identified two novel pro-tumorigenic roles (promoting cell survival and altering cell polarity) for genetic alterations of CTCF in endometrial cance
Long Range Magnetic Order and the Darwin Lagrangian
We simulate a finite system of confined electrons with inclusion of the
Darwin magnetic interaction in two- and three-dimensions. The lowest energy
states are located using the steepest descent quenching adapted for velocity
dependent potentials. Below a critical density the ground state is a static
Wigner lattice. For supercritical density the ground state has a non-zero
kinetic energy. The critical density decreases with for exponential
confinement but not for harmonic confinement. The lowest energy state also
depends on the confinement and dimension: an antiferromagnetic cluster forms
for harmonic confinement in two dimensions.Comment: 5 figure
ARPES study of Pb doped Bi_2Sr_2CaCu_2O_8 - a new Fermi surface picture
High resolution angle resolved photoemission data from Pb doped
Bi_2Sr_2CaCu_2O_8 (Bi2212) with suppressed superstructure is presented.
Improved resolution and very high momentum space sampling at various photon
energies reveal the presence of two Fermi surface pieces. One has the hole-like
topology, while the other one has its van Hove singularity very close to
(pi,0), its topology at some photon energies resembles the electron-like piece.
This result provides a unifying picture of the Fermi surface in the Bi2212
compound and reconciles the conflicting reports.Comment: 4 pages, 4 figure
Effect of Interband Transitions on the c axis Penetration Depth of Layered Superconductors
The electromagnetic response of a system with two planes per unit cell
involves, in addition to the usual intraband contribution, an added interband
term. These transitions affect the temperature dependence and the magnitude of
the zero temperature c-axis penetration depth. When the interplane hopping is
sufficiently small, the interband transitions dominate the low temperature
behaviour of the penetration depth which then does not reflect the linear
temperature dependence of the intraband term and in comparison becomes quite
flat even for a d-wave gap. It is in this regime that the pseudogap was found
in our previous normal state calculations of the c-axis conductivity, and the
effects are connected.Comment: 8 pages, 5 figure
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