6,751 research outputs found
Metastable π Junction between an s±-Wave and an s-Wave Superconductor
We examine a contact between a superconductor whose order parameter changes sign across the Brillioun zone, and an ordinary, uniform-sign superconductor. Within a Ginzburg-Landau-type model, we find that if the barrier between the two superconductors is not too high, the frustration of the Josephson coupling between different portions of the Fermi surface across the contact can lead to surprising consequences. These include time-reversal symmetry breaking at the interface and unusual energy-phase relations with multiple local minima. We propose this mechanism as a possible explanation for the half-integer flux quantum transitions in composite niobium-iron pnictide superconducting loops, which were discovered in recent experiments [C.-T. Chen et al., Nature Phys. 6, 260 (2010).]
Distilling entanglement from cascades with partial "Which Path" ambiguity
We develop a framework to calculate the density matrix of a pair of photons
emitted in a decay cascade with partial "which path" ambiguity. We describe an
appropriate entanglement distillation scheme which works also for certain
random cascades. The qualitative features of the distilled entanglement are
presented in a two dimensional "phase diagram". The theory is applied to the
quantum tomography of the decay cascade of a biexciton in a semiconductor
quantum dot. Agreement with experiment is obtained
Jahn-Teller Spectral Fingerprint in Molecular Photoemission: C60
The h_u hole spectral intensity for C60 -> C60+ molecular photoemission is
calculated at finite temperature by a parameter-free Lanczos diagonalization of
the electron-vibration Hamiltonian, including the full 8 H_g, 6 G_g, and 2 A_g
mode couplings. The computed spectrum at 800 K is in striking agreement with
gas-phase data. The energy separation of the first main shoulder from the main
photoemission peak, 230 meV in C60, is shown to measure directly and rather
generally the strength of the final-state Jahn-Teller coupling.Comment: 5 pages, 3 figure
Radiative cascade from quantum dot metastable spin-blockaded biexciton
We detect a novel radiative cascade from a neutral semiconductor quantum dot.
The cascade initiates from a metastable biexciton state in which the holes form
a spin-triplet configuration, Pauli-blockaded from relaxation to the
spin-singlet ground state. The triplet biexciton has two photon-phonon-photon
decay paths. Unlike in the singlet-ground state biexciton radiative cascade, in
which the two photons are co-linearly polarized, in the triplet biexciton
cascade they are crosslinearly polarized. We measured the two-photon
polarization density matrix and show that the phonon emitted when the
intermediate exciton relaxes from excited to ground state, preserves the
exciton's spin. The phonon, thus, does not carry with it any which-path
information other than its energy. Nevertheless, entanglement distillation by
spectral filtering was found to be rather ineffective for this cascade. This
deficiency results from the opposite sign of the anisotropic electron-hole
exchange interaction in the excited exciton relative to that in the ground
exciton.Comment: 6 pages, 4 figure
Comparison of different procedures to map reference evapotranspiration using geographical information systems and regression-based techniques
16 páginas, 6 figuras, 8 tablas.This paper compares different procedures for mapping reference evapotranspiration (ETo) by means of regression-based techniques and geographical information systems (GIS). ETo is calculated following the method of Hargreaves (HG) from a dense database of meteorological stations in the northernmost semi-arid region of Europe, the Ebro valley. The HG method requires the calculation of estimates of extraterrestrial radiation (Ra). We calculated this parameter using two approaches: (1) the common approach that assumes a planar surface and determines the parameter as a function of latitude and (2) using a digital terrain model (DTM) and GIS modelling. The maps were made on a monthly basis using both approaches. We also compared possible propagations of errors in the map calculations for maps derived from modelled layers of maximum and minimum temperatures with those modelled using previously determined local ETo calculations. We demonstrate that calculations of Ra from a DTM and GIS modelling provide a more realistic spatial distribution of ETo than those derived by only considering latitude. It is also preferable to model in advance the variables involved in the calculation of ETo (temperature and Ra) and to subsequently calculate ETo by means of layer algebra in the GIS rather than directly model the local ETo calculations. The obtained maps are useful for the purposes of agriculture and ecological and water resources management in the study area.This work has been supported by the project CGL2005-
04508/BOS financed by the Spanish Comission of Science
and Technology (CICYT) and FEDER, PIP176/2005
financed by the Aragón Government, and ‘Programa
de grupos de investigación consolidados’ (BOA 48 of
20-04-2005), also financed by the Aragón Government.
Research of the third author was supported by postdoctoral
fellowship by the Ministerio de Educación, Cultura
y Deporte (Spain).Peer reviewe
Distinguishable RGE running effects between Dirac neutrinos and Majorana neutrinos with vanishing Majorana CP-violating phases
In a novel parametrization of neutrino mixing and in the approximation of
-lepton dominance, we show that the one-loop renormalization-group
equations (RGEs) of Dirac neutrinos are different from those of Majorana
neutrinos even if two Majorana CP-violating phases vanish. As the latter can
keep vanishing from the electroweak scale to the typical seesaw scale, it makes
sense to distinguish between the RGE running effects of neutrino mixing
parameters in Dirac and Majorana cases. The differences are found to be quite
large in the minimal supersymmetric standard model with sizable ,
provided the masses of three neutrinos are nearly degenerate or have an
inverted hierarchy.Comment: 12 pages, 5 figure
Bi-Laplacian Growth Patterns in Disordered Media
Experiments in quasi 2-dimensional geometry (Hele Shaw cells) in which a
fluid is injected into a visco-elastic medium (foam, clay or
associating-polymers) show patterns akin to fracture in brittle materials, very
different from standard Laplacian growth patterns of viscous fingering. An
analytic theory is lacking since a pre-requisite to describing the fracture of
elastic material is the solution of the bi-Laplace rather than the Laplace
equation. In this Letter we close this gap, offering a theory of bi-Laplacian
growth patterns based on the method of iterated conformal maps.Comment: Submitted to PRL. For further information see
http://www.weizmann.ac.il/chemphys/ander
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