5,628 research outputs found
Electric field effect on superconductivity at complex oxide interfaces
We examine the enhancement of the interfacial superconductivity between
LaAlO and SrTiO by an effective electric field. Through the
breaking of inversion symmetry at the interface, we show that a term coupling
the superfluid density and an electric field can augment the superconductivity
transition temperature. Microscopically, we show that an electric field can
also produce changes in the carrier density by relating the measured
capacitance to the density of states. Through the electron-phonon induced
interaction in bulk SrTiO, we estimate the transition temperature.Comment: 7 Pages, Submitted to Physical Revie
Thermodynamic properties of Bi2Sr2CaCu2O8 calculated from the electronic dispersion
The electronic dispersion for Bi2Sr2CaCu2O(8+d) has been determined from
angle-resolved photoelectron spectroscopy (ARPES). From this dispersion we
calculate the entropy and superfluid density. Even with no adjustable
parameters we obtain an exceptional match with experimental data across the
entire phase diagram, thus indirectly confirming both the ARPES and
thermodynamic data. The van Hove singularity is crossed in the overdoped region
giving a distinctive linear-in-T temperature dependence in the superfluid
density there.Comment: 5 pages, 4 figures, submitted to Physical Review Letter
Induced polarization at a paraelectric/superconducting interface
We examine the modified electronic states at the interface between
superconducting and ferro(para)-electric heterostructures. We find that
electric polarization and superconducting order parameters can be
significantly modified due to coupling through linear terms brought about by
explicit symmetry breaking at the interface. Using an effective action and a
Ginzburg-Landau formalism, we show that an interaction term linear in the
electric polarization will modify the superconducting order parameter at
the interface. This also produces modulation of a ferroelectric polarization.
It is shown that a paraelectric-superconductor interaction will produce an
interface-induced ferroelectric polarization.Comment: 4 pages, 3 figures, Submitted to Phys. Rev.
Quasiparticles and Energy Scaling in BiSrCaCuO (=1-3): Angle-Resolved Photoemission Spectroscopy
Angle-resolved photoemission spectroscopy (ARPES) has been performed on the
single- to triple-layered Bi-family high-{\it T} superconductors
(BiSrCaCuO, =1-3). We found a sharp
quasiparticle peak as well as a pseudogap at the Fermi level in the
triple-layered compound. Comparison among three compounds has revealed a
universal rule that the characteristic energies of superconducting and
pseudogap behaviors are scaled with the maximum {\it T}.Comment: 4 pages, 4 figure
Radial Velocities of Six OB Stars
We present new results from a radial velocity study of six bright OB stars
with little or no prior measurements. One of these, HD 45314, may be a
long-period binary, but the velocity variations of this Be star may be related
to changes in its circumstellar disk. Significant velocity variations were also
found for HD 60848 (possibly related to nonradial pulsations) and HD 61827
(related to wind variations). The other three targets, HD 46150, HD 54879, and
HD 206183, are constant velocity objects, but we note that HD 54879 has
H emission that may originate from a binary companion. We illustrate
the average red spectrum of each target.Comment: Accepted for publication in PASP July 2007 issu
Weak Values with Decoherence
The weak value of an observable is experimentally accessible by weak
measurements as theoretically analyzed by Aharonov et al. and recently
experimentally demonstrated. We introduce a weak operator associated with the
weak values and give a general framework of quantum operations to the W
operator in parallel with the Kraus representation of the completely positive
map for the density operator. The decoherence effect is also investigated in
terms of the weak measurement by a shift of a probe wave function of continuous
variable. As an application, we demonstrate how the geometric phase is affected
by the bit flip noise.Comment: 17 pages, 3 figure
Multi-objective engineering shape optimization using differential evolution interfaced to the Nimrod/O tool
This paper presents an enhancement of the Nimrod/O optimization tool by interfacing DEMO, an external multiobjective optimization algorithm. DEMO is a variant of differential evolution – an algorithm that has attained much popularity in the research community, and this work represents the first time that true multiobjective optimizations have been performed with Nimrod/O. A modification to the DEMO code enables multiple objectives to be evaluated concurrently. With Nimrod/O’s support for parallelism, this can reduce the wall-clock time significantly for compute intensive objective function evaluations. We describe the usage and implementation of the interface and present two optimizations. The first is a two objective mathematical function in which the Pareto front is successfully found after only 30 generations. The second test case is the three-objective shape optimization of a rib-reinforced wall bracket using the Finite Element software, Code_Aster. The interfacing of the already successful packages of Nimrod/O and DEMO yields a solution that we believe can benefit a wide community, both industrial and academic
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