119 research outputs found
Cryogenic Calibration Setup for Broadband Complex Impedance Measurements
Reflection measurements give access to the complex impedance of a material on
a wide frequency range. This is of interest to study the dynamical properties
of various materials, for instance disordered superconductors. However
reflection measurements made at cryogenic temperature suffer from the
difficulty to reliably subtract the circuit contribution. Here we report on the
design and first tests of a setup able to precisely calibrate in situ the
sample reflection, at 4.2 K and up to 2 GHz, by switching and measuring, during
the same cool down, the sample and three calibration standards.Comment: (6 pages, 6 figures
Ferromagnetic 0-pi Junctions as Classical Spins
The ground state of highly damped PdNi based 0-pi ferromagnetic Josephson
junctions shows a spontaneous half quantum vortex, sustained by a supercurrent
of undetermined sign. This supercurrent flows in the electrode of a Josephson
junction used as a detector and produces a phi(0)/4 shift in its magnetic
diffraction pattern. We have measured the statistics of the positive or
negative sign shift occurring at the superconducting transition of such a
junction. The randomness of the shift sign, the reproducibility of its
magnitude and the possibility of achieving exact flux compensation upon field
cooling: all these features show that 0-pi junctions behave as classical spins,
just as magnetic nanoparticles with uniaxial anisotropy.Comment: 4 pages, 4 figure
High-Quality Planar high-Tc Josephson Junctions
Reproducible high-Tc Josephson junctions have been made in a rather simple
two-step process using ion irradiation. A microbridge (1 to 5 ?m wide) is
firstly designed by ion irradiating a c-axis-oriented YBa2Cu3O7-? film through
a gold mask such as the non-protected part becomes insulating. A lower Tc part
is then defined within the bridge by irradiating with a much lower fluence
through a narrow slit (20 nm) opened in a standard electronic photoresist.
These planar junctions, whose settings can be finely tuned, exhibit
reproducible and nearly ideal Josephson characteristics. This process can be
used to produce complex Josephson circuits.Comment: 4 pages, 5 figures, to be published in Applied Physics Letter
Studi Eksplorasi Minat Beli Mobil Listrik pada Generasi Milenial
This study aims to find out what factors that influence the purchase intention of electric vehicles on millennials in Jabodetabek and what factors contribute the most to the purchase intention. The sample and population in this study were 334 millennials in Jabodetabek using the purposive sampling method and distributing questionnaires through various social media platforms. This study uses the theory of TAM and TPB with the analytical method through Exploratory Factor Analysis (EFA) approach and linear regression analysis to process the data through SPSS 25. The result of the study found that there were nine factors that influence the purchase intention of electric cars on millennials in Jabodetabek. The ninth factor is product knowledge, perceived behavioral control, price and advertising, social influence, product perception, environmental concern, ease of use, perceived benefits, and costs. Among the nine factors, price and advertising are the factors that contribute most to the purchase intention. It is hoped that this study can be used by electric car manufacturers as a basis for developing marketing and sales strategies through consumer purchase intention
Two-dimensional Ising model with competing interactions and its application to clusters and arrays of -rings and adiabatic quantum computing
We study planar clusters consisting of loops including a Josephson
-junction (-rings). Each -ring carries a persistent current and
behaves as a classical orbital moment. The type of particular state associated
with the orientation of orbital moments at the cluster depends on the
interaction between these orbital moments and can be easily controlled, i.e. by
a bias current or by other means. We show that these systems can be described
by the two-dimensional Ising model with competing nearest-neighbor and diagonal
interactions and investigate the phase diagram of this model. The
characteristic features of the model are analyzed based on the exact solutions
for small clusters such as a 5-site square plaquette as well as on a mean-field
type approach for the infinite square lattice of Ising spins. The results are
compared with spin patterns obtained by Monte Carlo simulations for the 100
100 square lattice and with experiment. We show that the -ring
clusters may be used as a new type of superconducting memory elements. The
obtained results may be verified in experiments and are applicable to adiabatic
quantum computing where the states are switched adiabatically with the slow
change of coupling constants.Comment: 32 pages, 22 figures, RevTe
High Tc Josephson nanoJunctions made by ion irradiation : characteristics and reproducibility
Reproducible High Tc Josephson junctions have been made in a rather simple
two-step process using ion irradiation. A microbridge 1 to 5 micrometers wide
is firstly designed by ion irradiating a c-axis-oriented YBa2Cu3O7 film through
a gold mask such as the unprotected part becomes insulating. A lower Tc part is
then defined within the bridge by irradiating with a much lower dose through a
20 nm wide narrow slit opened in a standard electronic photoresist. These
planar junctions, whose settings can be finely tuned, exhibit reproducible and
nearly ideal Josephson characteristics. Non hysteretic Resistively Shunted
Junction (RSJ) like behavior is observed, together with sinc Fraunhofer
patterns for rectangular junctions. The IcRn product varies with temperature ;
it can reach a few mV. The typical resistance ranges from 0.1 to a few ohms,
and the critical current density can be as high as 30 kA/cm2. The dispersion in
characteristics is very low, in the 5% to 10% range. Such nanojunctions have
been used to make microSQUIDs (Superconducting Quantum Interference Device)
operating at Liquid Nitrogen (LN2) temperature. They exhibit a very small
asymmetry, a good sensitivity and a rather low noise. The process is easily
scalable to make rather complex Josephson circuits.Comment: 4 pages, 5 figures, Applied Superconductivity Conference Seattle 200
Interaction-driven quantum phase transition of a single magnetic impurity in Fe(Se,Te)
Understanding the interplay between individual magnetic impurities and
superconductivity is crucial for bottom-up construction of novel phases of
matter. For decades, the description by Yu, Shiba and Rusinov (YSR) of single
spins in a superconductor and its extension to include quantum effects has
proven highly successful: the pair-breaking potential of the spin generates
sub-gap electron- and hole excitations that are energetically equidistant from
zero. By tuning the energy of the sub-gap states through zero, the impurity
screening by the superconductor makes the ground state gain or lose an
electron, signalling a parity breaking quantum phase transition. Here we show
that in multi-orbital impurities, correlations between the in-gap states can
conversely lead to a quantum phase transition where more than one electron
simultaneously leave the impurity without significant effect of the screening
by the superconductor, while the parity may remain unchanged. This finding
implies that the YSR treatment is not always valid, and that intra-atomic
interactions, particularly Hund's coupling that favours high spin
configurations, are an essential ingredient for understanding the sub-gap
states. The interaction-driven quantum phase transition should be taken into
account for impurity-based band-structure engineering, and may provide a
fruitful basis in the search for novel physics.Comment: Main text and supplementar
Phase Separation and the Phase Diagram in Cuprates Superconductors
We show that the main features of the cuprates superconductors phase diagram
can be derived considering the disorder as a key property of these materials.
Our basic point is that the high pseudogap line is an onset of phase separation
which generates compounds made up of regions with distinct doping levels. We
calculate how this continuous temperature dependent phase separation process
occurs in high critical temperature superconductors (HTSC) using the
Cahn-Hilliard approach, originally applied to study alloys. Since the level of
phase separation varies for different cuprates, it is possible that different
systems with average doping level pm exhibit different degrees of charge and
spin segregation. Calculations on inhomogeneous charge distributions in form of
stripes in finite clusters performed by the Bogoliubov-deGennes superconducting
approach yield good agreement to the pseudogap temperature T*(pm), the onset of
local pairing amplitudes with phase locked and concomitantly, how they develop
at low temperatures into the superconducting phase at Tc(pm) by percolation.Comment: 9 pages, 9 figures. Submitted to Phys. Rev.
Future Precision Neutrino Oscillation Experiments and Theoretical Implications
Future neutrino oscillation experiments will lead to precision measurements
of neutrino mass splittings and mixings. The flavour structure of the lepton
sector will therefore at some point become better known than that of the quark
sector. This article discusses the potential of future oscillation experiments
on the basis of detailed simulations with an emphasis on experiments which can
be done in about ten years. In addition, some theoretical implications for
neutrino mass models will be briefly discussed.Comment: Talk given at Nobel Symposium 2004: Neutrino Physics, Haga Slott,
Enkoping, Sweden, 19-24 Aug 200
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