303 research outputs found
Growth of Single Unit-Cell Superconducting LaSrCuO Films
We have developed an approach to grow high quality ultrathin films of
LaSrCuO with molecular beam epitaxy, by adding a
homoepitaxial buffer layer in order to minimize the degradation of the film
structure at the interface. The advantage of this method is to enable a further
reduction of the minimal thickness of a superconducting
LaSrCuO film. The main result of our work is that a
single unit cell (only two copper oxide planes) grown on a SrLaAlO
substrate exhibits a superconducting transition at 12.5 K (zero resistance) and
an in-plane magnetic penetration depth = 535 nm.Comment: to be published in "Solid State Electonics" special issue, conference
proceedings of the 9th Workshop on Oxide Electronics, St-Pete Beach, FL,
20-23 november 2002 : 12 pages 4 figures in preprint versio
Domain growth of Dy2O3 buffer layers on SrTiO3
Dy2O3 layers have been grown on SrTiO3 by molecular beam epitaxy. X-ray and electron diffraction patterns clearly show that Dy2O3 grows epitaxially on SrTiO3 with {100} planes parallel to the substrate surface. Transmission electron microscopy reveals that the Dy2O3 film breaks up into small domains (10-40 nm). This leads to the formation of terraces which limits the structural perfection of thin overgrown DyBa2Cu3O7 by introducing steps and small misorientations (within 3°). The resulting surface corrugation does not preclude the growth of epitaxial c-axis DyBa2Cu3O7 films with a Tc0 of 86 K. Crystallographic analysis and image calculations show that the domain growth of Dy2O3 is associated with the formation of 90° rotation twin
Comparison of two types of synchronization of external-cavity semiconductor lasers
Missatge de l'editorial: "This paper was published in Optical letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-27-1-31. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law."We study numerically the synchronization of external-cavity semiconductor lasers in a master–slave configuration, based on a Lang–Kobayashi-type model. Depending on the feedback and coupling strengths, the slave laser synchronizes with the injected optical field or with the injected field but lags in time. We show that these two types of synchronization present different robustness with respect to the noise, frequency detuning, and current modulation of the master laser.Peer ReviewedPostprint (published version
Lag time and parameter mismatches in synchronization of unidirectionally coupled chaotic external cavity semiconductor lasers
We report an analysis of synchronization between two unidirectionally coupled
chaotic external cavity master/slave semiconductor lasers with two
characteristic delay times, where the delay time in the coupling is different
from the delay time in the coupled systems themselves. We demonstrate for the
first time that parameter mismatches in photon decay rates for the master and
slave lasers can explain the experimental observation that the lag time is
equal to the coupling delay time.Comment: LaTex, 5 pages, submitted to PRE(R
Gigantic anisotropic uniaxial pressure effect on superconductivity within the CuO2 plane of La1.64Eu0.2Sr0.16CuO4 - strain control of stripe criticality
The effect of uniaxial pressure on superconductivity was examined for a
high-Tc cuprate La1.64Eu0.2Sr0.16CuO4, which is located at the boundary between
the superconducting and stripe phases. We found remarkably large anisotropy of
the uniaxial pressure effect not only between the in-plane and out-of-plane
pressures but also within the CuO2-plane. When the pressure is applied along
the tetragonal [110] direction, we found the largest pressure effect ever
observed in cuprates, dTc/dP - 2.5 K/kbar, while the change of Tc was not
appreciable when applied along [100]. This substantial in-plane anisotropy is
attributed to an intimate link between the symmetry of the one-dimensional
stripes and that of the strain produced within the CuO2 plane.Comment: 4 pages including 3 figure
On possible superconductivity in the doped ladder compound La_(1-x)Sr_xCuO_2.5
LaCuO_2.5 is a system of coupled, two-chain, cuprate ladders which may be
doped systematically by Sr substitution. Motivated by the recent synthesis of
single crystals, we investigate theoretically the possibility of
superconductivity in this compound. We use a model of spin fluctuation-mediated
superconductivity, where the pairing potential is strongly peaked at \pi in the
ladder direction. We solve the coupled gap equations on the bonding and
antibonding ladder bands to find superconducting solutions across the range of
doping, and discuss their relevance to the real material.Comment: RevTex, 4 pages, 7 figure
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