Search results for "Coherence length"
showing 10 items of 30 documents
Gauge theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets
2017
We present the generalized quasiclassical theory of the long-range superconducting proximity effect in heterostructures with strong ferromagnets, where the exchange splitting is of the order of Fermi energy. In the ferromagnet the propagation of equal-spin Cooper pairs residing on the spin-split Fermi surfaces is shown to be governed by the spin-dependent Abelian gauge field which results either from the spin-orbital coupling or from the magnetic texture. This additional gauge field enters into the quasiclassical equations in superposition with the usual electromagnetic vector potential and results in the generation of spontaneous superconducting currents and phase shifts in various geometr…
Spatial information transmission using orthogonal mutual coherence coding.
2005
We use the coherence of a light beam to encode spatial information. We apply this principle to obtain spatial superresolution in a limited aperture system. The method is based on shaping the mutual intensity function of the illumination beam in a set of orthogonal distributions, each one carrying the information for a different frequency bandpass or spatial region of the input object. The coherence coding is analogous to time multiplexing but with multiplexing time slots that are given by the coherence time of the illumination beam. Most images are static during times much longer than this coherence time, and thus the increase of resolution in our system is obtained without any noticeable c…
Observation of classical optical wave condensation
2010
We demonstrate the nonlinear condensation of classical optical waves. The condensation is observed directly, as a function of nonlinearity and wave kinetic energy, in a self-defocusing photorefractive crystal.
The electron gas with short coherence length pairs: how to approach the stronger coupling limit?
2001
Abstract The attractive Hubbard model is investigated in 2D using a T -matrix approach. In a self-consistent calculation pairs as infinite lifetime Bosons only exist in the atomic limit and therefore a Fermi surface can be investigated also in the stronger coupling regime. A heavy quasiparticle peak with a weak dispersion crosses the Fermi surface at k F whereas light, single particle excitations do only exist far away from the Fermi surface. At low temperatures there seem to exist different self-consistent solutions. In one of them a pseudogap opens even in the integrated density of states. In the present work accurate k -dependent and k -integrated spectral quantities for a 2D finite latt…
Monte Carlo study of cluster-diameter distribution: An observable to estimate correlation lengths
1997
We report numerical simulations of two-dimensional $q$-state Potts models with emphasis on a new quantity for the computation of spatial correlation lengths. This quantity is the cluster-diameter distribution function $G_{diam}(x)$, which measures the distribution of the diameter of stochastically defined cluster. Theoretically it is predicted to fall off exponentially for large diameter $x$, $G_{diam} \propto \exp(-x/\xi)$, where $\xi$ is the correlation length as usually defined through the large-distance behavior of two-point correlation functions. The results of our extensive Monte Carlo study in the disordered phase of the models with $q=10$, 15, and $20$ on large square lattices of si…
Perpendicular transport properties of YBa_2Cu_3O_{7-\delta}/PrBa_2Cu_3O_{7-\delta} superlattices
2000
The coupling between the superconducting planes of YBa2Cu3O{7-\delta}/ PrBa2Cu3O{7-\delta} superlattices has been measured by c-axis transport. We show that only by changing the thickness of the superconducting YBa2Cu3O{7-\delta} layers, it is possible to switch between quasi-particle and Josephson tunneling. From our data we deduce a low temperature c-axis coherence length of 0.27 nm.
Microwave surface impedance of proximity-coupled superconducting (Nb)/spin-glass (CuMn) bilayers
1998
The surface impedance of Nb/CuMn (superconducting/spin-glass) bilayers has been measured at 10 GHz with the parallel plate resonator technique to obtain information about the exotic behavior of the order parameter in superconducting/magnetic proximity systems. The data strongly differs from the superconducting/normal-metal case, showing the magnetic nature of the CuMn layer, which acts as a weak ferromagnet. The results are described in the framework of two models for the electrodynamics of superconducting/ferromagnetic (S/M) bilayers characterized by a proximity-coupling length scale which is independent of temperature.
Neutron scattering study of melting ofHe3surface layers
1982
The melting of the incommensurate phase of $^{3}\mathrm{He}$ submonolayers adsorbed on Grafoil was investigated by elastic neutron scattering. The temperature dependence of the nearest-neighbor distance, the coherence length, and the peak intensity of the structure factor can be explained by a simple model assuming a melting transition which is driven by thermally created lattice defects.
Low-damping spin-wave propagation in a micro-structured Co2Mn0.6Fe0.4Si Heusler waveguide
2012
We report on the investigation of spin-wave propagation in a micro-structured Co2Mn0.6Fe0.4Si (CMFS) Heusler waveguide. The reduced magnetic losses of this compound compared to the commonly used Ni81Fe19 allow for the observation of spin-wave propagation over distances as high as 75 μm via Brillouin light scattering (BLS) microscopy. In the linear regime, a maximum decay length of 16.7 μm of the spin-wave amplitude was found. The coherence length of the observed spin-wave modes was estimated to be at least 16 μm via phase-resolved BLS techniques.
Spatial information transmission using axial temporal coherence coding
2007
We present an approach that can be used for transmission of information through space-limited systems or for superresolution. The spatial information is coded with different axial temporal coherence by interfering every spatial region in the input with the same region, but with a certain known delay in the longitudinal axis. Every spatial region has different delay. After mixing all of the spatial information, it is transmitted through the space-limited system. At the detection the information is passed through a similar interference setup containing certain axial delay. By temporally scanning along the longitudinal axis, each time a different spatial region that was coded with the correspo…