357 research outputs found
Multi-layer atom chips for versatile atom micro manipulation
We employ a combination of optical UV- and electron-beam-lithography to
create an atom chip combining sub-micron wire structures with larger
conventional wires on a single substrate. The new multi-layer fabrication
enables crossed wire configurations, greatly enhancing the flexibility in
designing potentials for ultra cold quantum gases and Bose-Einstein
condensates. Large current densities of >6 x 10^7 A/cm^2 and high voltages of
up to 65 V across 0.3 micron gaps are supported by even the smallest wire
structures. We experimentally demonstrate the flexibility of the next
generation atom chip by producing Bose-Einstein condensates in magnetic traps
created by a combination of wires involving all different fabrication methods
and structure sizes.Comment: 4 pages, 5 figure
Resistive state of superconducting structures with fractal clusters of a normal phase
The effect of morphologic factors on magnetic flux dynamics and critical
currents in percolative superconducting structures is considered. The
superconductor contains the fractal clusters of a normal phase, which act as
pinning centers. The properties of these clusters are analyzed in the general
case of gamma-distribution of their areas. The statistical characteristics of
the normal phase clusters are studied, the critical current distribution is
derived, and the dependencies of the main statistical parameters on the fractal
dimension are found. The effect of fractal clusters of a normal phase on the
electric field induced by the motion of the magnetic flux after the vortices
have been broken away from pinning centers is considered. The voltage-current
characteristics of fractal superconducting structures in a resistive state for
an arbitrary fractal dimension are obtained. It is found that the fractality of
the boundaries of normal phase clusters intensifies magnetic flux trapping and
thereby increases the current-carrying capability of the superconductor.Comment: 15 pages with 8 figures, revtex3, alternative e-mail of author is
[email protected]
Anomalous specific heat jump in the heavy fermion superconductor CeCoIn
We study the anomalously large specific heat jump and its systematic change
with pressure in CeCoIn superconductor. Starting with the general free
energy functional of the superconductor for a coupled electron boson system, we
derived the analytic result of the specific heat jump of the strong coupling
superconductivity occurring in the coupled electron boson system. Then using
the two component spin-fermion model we calculate the specific heat coefficient
both for the normal and superconducting states and show a good
agreement with the experiment of CeCoIn. Our result also clearly
demonstrated that the specific heat coefficient of a coupled electron
boson system can be freely interpreted as a renormalization either of the
electronic or of the bosonic degrees of freedom.Comment: 5 pages, 2 figure
Do I-Pass for FAIR?:A self-assessment tool to measure the FAIR-ness of an organization
The 15 FAIR data principles are intended to be applied to a dataset, but the acronym FAIR is also used as an adjective for other (digital) matters, such as FAIR data stewardship, FAIR data infrastructure and FAIR data services. Moreover, in the context of Open Science and scientific integrity, more and more Dutch universities and research organizations discuss a FAIR organization as an important goal, thus implementing RDM practices and support with the FAIR principles as a main driver.
Triggered by this use of the acronym FAIR for organizations, an LCRDM (National Coordination Point Research Data Management) task group explored the definition, characteristics and principles of a so-called âFAIR enabling organizationâ. The task group delivered two products: (1) a definition for a FAIR enabling organization and (2) a self-assessment tool to evaluate the FAIR-ness of a research organization (research institute, university or university of applied sciences).
This self-assessment tool is a simple instrument, presented in an editable PDF form. By answering the questions and evaluating the level (beginner, intermediate, or advanced) at which you assess the performance of your organization, you will be able to define the actual FAIR-ness. In addition you can define a Road Map to become a FAIR Enabling Research Organization using the information in de more advances level(s)
Two-Particle Interference with Double Twin-Atom Beams
We demonstrate a source for correlated pairs of atoms characterized by two
opposite momenta and two spatial modes forming a Bell state only involving
external degrees of freedom. We characterize the state of the emitted atom
beams by observing strong number squeezing up to -10 dB in the correlated
two-particle modes of emission. We furthermore demonstrate genuine two-particle
interference in the normalized second-order correlation function
relative to the emitted atoms.Comment: 6 pages, 3 figure
Dynamics of the magnetic flux trapped in fractal clusters of normal phase in a superconductor
The influence of geometry and morphology of superconducting structure on
critical currents and magnetic flux trapping in percolative type-II
superconductor is considered. The superconductor contains the clusters of a
normal phase, which act as pinning centers. It is found that such clusters have
significant fractal properties. The main features of these clusters are studied
in detail: the cluster statistics is analyzed; the fractal dimension of their
boundary is estimated; the distribution of critical currents is obtained, and
its peculiarities are explored. It is examined thoroughly how the finite
resolution capacity of the cluster geometrical size measurement affects the
estimated value of fractal dimension. The effect of fractal properties of the
normal phase clusters on the electric field arising from magnetic flux motion
is investigated in the case of an exponential distribution of cluster areas.
The voltage-current characteristics of superconductors in the resistive state
for an arbitrary fractal dimension are obtained. It is revealed that the
fractality of the boundaries of the normal phase clusters intensifies the
magnetic flux trapping and thereby raises the critical current of a
superconductor.Comment: revtex, 16 pages with 1 table and 5 figures; text and figures are
improved; more detailed version with geometric probability analisys of the
distribution of entry points into weak links over the perimeter of a normal
phase clusters and one additional figure is published in Phys.Rev.B;
alternative e-mail of author is [email protected]
Electron Dynamics in NdCeCuO: Evidence for the Pseudogap State and Unconventional c-axis Response
Infrared reflectance measurements were made with light polarized along the a-
and c-axis of both superconducting and antiferromagnetic phases of electron
doped NdCeCuO. The results are compared to
characteristic features of the electromagnetic response in hole doped cuprates.
Within the CuO planes the frequency dependent scattering rate,
1/, is depressed below 650 cm; this behavior is a
hallmark of the pseudogap state. While in several hole doped compounds the
energy scales associated with the pseudogap and superconducting states are
quite close, we are able to show that in NdCeCuO
the two scales differ by more than one order of magnitude. Another feature of
the in-plane charge response is a peak in the real part of the conductivity,
, at 50-110 cm which is in sharp contrast with the
Drude-like response where is centered at . This
latter effect is similar to what is found in disordered hole doped cuprates and
is discussed in the context of carrier localization. Examination of the c-axis
conductivity gives evidence for an anomalously broad frequency range from which
the interlayer superfluid is accumulated. Compelling evidence for the pseudogap
state as well as other characteristics of the charge dynamics in
NdCeCuO signal global similarities of the cuprate
phase diagram with respect to electron and hole doping.Comment: Submitted to PR
Elastic Chiral Waveguides with Gyro-Hinges
This article presents a novel chiral structure, consisting of EulerâBernoulli beams connected to gyroscopic spinners.Anew type of boundary condition is introduced, which is referred to as a gyrohinge. In this system, flexural waves are coupled with rotational motion.Time-harmonic conditions are derived by assuming small nutation angles of the spinners. It is shown that the eigenfrequencies of a finite beam with gyro-hinges at one or both ends change dramatically with the moments of inertia and the spin and precession rates of the spinners. The formulation is then extended to elastic beams with periodically-spaced gyro-hinges, whose dispersion properties are investigated in detail. In particular, it is shown how stop-bands and standing modes are affected by the introduction of gyroscopic spinners at the junctions. It is also demonstrated that a periodic system composed of beams connected by gyro-hinges represents a good approximation of a gyrobeam, a theoretical structural element consisting of an elastic beam possessing a continuous distribution of stored angular momentum. The gyricity coefficient of a gyrobeam is then interpreted in terms of the physical parameters of the system of beams with gyroscopic spinners. This article opens a new perspective on the design and practical implementation of chiral mechanical systems
Developments in the negative-U modelling of the cuprate HTSC systems
The paper deals with the many stands that go into creating the unique and
complex nature of the HTSC cuprates above Tc as below. Like its predecessors it
treats charge, not spin or lattice, as prime mover, but thus taken in the
context of the chemical bonding relevant to these copper oxides. The crucial
shell filling, negative-U, double-loading fluctuations possible there require
accessing at high valent local environment as prevails within the mixed valent,
inhomogeneous two sub-system circumstance of the HTSC materials. Close
attention is paid to the recent results from Corson, Demsar, Li, Johnson,
Norman, Varma, Gyorffy and colleagues.Comment: 44 pages:200+ references. Submitted to J.Phys.:Condensed Matter, Sept
7 200
A monotone multigrid solver for two body contact problems in biomechanics
The purpose of the paper is to apply monotone multigrid methods to static and dynamic biomechanical contact problems. In space, a finite element method involving a mortar discretization of the contact conditions is used. In time, a new contact-stabilized Newmark scheme is presented. Numerical experiments for a two body Hertzian contact problem and a biomechanical application are reported
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