2,691 research outputs found
Broadening of the Berezinskii-Kosterlitz-Thouless transition by correlated disorder
The Berezinskii-Kosterlitz-Thouless (BKT) transition in two-dimensional superconductors is usually expected to be protected against disorder. However, its fingerprints in a real system, such as, e.g., the universal superfluid- density jump, are often at odds with this expectation. Here, we show that the disorder-induced granularity of the superconducting state modifies the nucleation mechanism for vortex-antivortex pairs. This leads to a considerable smearing of the universal superfluid-density jump as compared to the paradigmatic clean case, in agreement with experimental observations
BKT universality class in the presence of correlated disorder
The correct detection of the Berezinskii-Kosterlitz-Thouless (BKT) transition
in quasi-two-dimensional superconductors still remains a controversial issue.
Its main signatures, indeed, are often at odds with the theoretical
expectations. In a recent work\cite{me} we have shown that the presence of
spatially correlated disorder plays a key role in this sense being it the
reason underlying the experimentally-observed smearing of the universal
superfluid-density jump. In the present paper, we closely investigate the
effects of correlated disorder on the BKT transition, addressing specifically
the issue whether it changes or not the BKT universality class.Comment: The present paper has already been submitted as Special Issue
"Proceedings of the conference SuperFluctuations 2017
Unconventional dc transport in Rashba electron gases
We discuss the transport properties of a disordered two-dimensional electron
gas with strong Rashba spin-orbit coupling. We show that in the high-density
regime where the Fermi energy overcomes the energy associated with spin-orbit
coupling, dc transport is accurately described by a standard Drude's law, due
to a non-trivial compensation between the suppression of back-scattering and
the relativistic correction to the quasi-particle velocity. On the contrary,
when the system enters the opposite dominant spin-orbit regime, Drude's
paradigm breaks down and the dc conductivity becomes strongly sensitive to the
spin-orbit coupling strength, providing a suitable tool to test the
entanglement between spin and charge degrees of freedom in theseComment: 6 pages, 4 figures+Supplemental Material. To appear in Phys. Rev.
Let
Disordered XY model: effective medium theory and beyond
We study the effect of uncorrelated random disorder on the temperature
dependence of the superfluid stiffness in the two-dimensional classical XY
model. By means of a perturbative expansion in the disorder potential,
equivalent to the T-matrix approximation, we provide an extension of the
effective-medium-theory result able to describe the low-temperature stiffness,
and its separate diamagnetic and paramagnetic contributions. These analytical
results provide an excellent description of the Monte Carlo simulations for two
prototype examples of uncorrelated disorder. Our findings offer an interesting
perspective on the effects of quenched disorder on longitudinal phase
fluctuations in two-dimensional superfluid systems.Comment: 11 pages, 5 figure
Comparison of osmotic dehydration of Dixiland and Elegant Lady peach slices in glucose and sucrose solutions
PosterPeach (Prunus persica) is a stone fruit with a fleshy pulp and a delicate aroma. Peach provides vitamins, fiber and antioxidant compounds, among others. Nevertheless, it is a perishable fruit. Dried fruit (D) is a strategy to maintain the provision of this healthy fruit during the whole year. Osmotic dehydration (OD) previous conventional drying is a pre treatment applied to fresh fruit in order to prevent browning or sugar caramelization during prolonged hot air exposure. Here, the effects of sugar type and cultivar on the nutritional and nutraceutical properties were studied using slices of peach of two commercial cultivars Dixiland (DX) and Elegant Lady (EL) using OD with sucrose or glucose as a pretreatment before conventional drying (D)EEA San PedroFil: Salvañal, Lara. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro de Estudios FotosintĂ©ticos y BioquĂmicos; ArgentinaFil: Salvañal, Lara. Universidad Nacional de Rosario. Facultad de Ciencias BioquĂmicas y FarmacĂ©uticas. Centro de Estudios FotosintĂ©ticos y BioquĂmicos; ArgentinaFil: Gabilondo, Julieta. Instituto Nacional de TecnologĂa Agropecuaria (INTA). EstaciĂłn Experimental Agropecuaria San Pedro; ArgentinaFil: Budde, Claudio Olaf. Instituto Nacional de TecnologĂa Agropecuaria (INTA). EstaciĂłn Experimental Agropecuaria San Pedro; ArgentinaFil: Corbino, Graciela Beatriz. Instituto Nacional de TecnologĂa Agropecuaria (INTA). EstaciĂłn Experimental Agropecuaria San Pedro; ArgentinaFil: Lara, MarĂa Valeria. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro de Estudios FotosintĂ©ticos y BioquĂmicos; ArgentinaFil: Lara, MarĂa Valeria.Universidad Nacional de Rosario. Facultad de Ciencias BioquĂmicas y FarmacĂ©uticas. Centro de Estudios FotosintĂ©ticos y BioquĂmicos; Argentin
Generalized Josephson plasmons in bilayer superconductors
Layered superconductors like High-Tc cuprates display out-of-plane plasma
oscillations between layers sustained by the weak Josephson coupling among the
superconducting sheets, the so-called Josephson plasmons. Bilayer cuprates
hosts two of such modes, but due to the anisotropy of the electronic response
their description at generic wavevector cannot be separated from that of the
in-plane oscillations. In this paper we provide an analytical theoretical
framework able to describe the dispersions and the polarizations of the
generalized plasma modes of such systems, that has been only partly addressed
by previous work in the literature. We then employ it to explain the peculiar
characteristics of their linear optical response, by providing a fully
microscopic explanation for the appearance of a finite-frequency peak in the
real part of the optical conductivity. On a wider perspective, the complete
characterization of the Josephson plasma modes provided by our approach
represents a groundwork to address open issues raised by recent experiments
with strong THz pulses, able to drive them beyond the linear-response regime.Comment: 21 pages, 8 figure
Charge density response in layered metals: retardation effects, generalized plasma waves and their spectroscopic signatures
Transverse plasma polaritons and longitudinal plasmons describe the
propagation of light-matter modes in an isotropic metal. However, in a layered
metal the anisotropy of the bare electromagnetic response mixes the
longitudinal and transverse excitations, making the distinction between
polariton and plasmon blurred at small wavevectors, where retardation effects
of the electromagnetic interactions become quantitatively relevant. In the
usual Kubo approach for the linear response, this effect appears as a mixing
between the density and the transverse current fluctuations, that requires to
revise the standard RPA approach for density correlations where only the
instantaneous Coulomb potential is included. In this paper we derive the
general expression for the density and current correlation functions at long
wavelength in a layered metal, showing that below a crossover scale set by the
anisotropy of the plasma frequencies retardation effects make the dispersion of
the generalized plasma modes different from the standard RPA result. In
addition, the mixed longitudinal and transverse nature of these excitations
reflects in a double-peak structure for the density response, that can be
eventually accessed by means of high-momentum resolution electron-energy-loss
or X-rays spectroscopies.Comment: 22 pages, 3 figure
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