3,163 research outputs found
Thermally induced 0-pi phase transition in Josephson junctions through a ferromagnetic oxide film
We investigate the Josephson transport through a ferromagnetic oxide film,
e.g., LaBaCuO, theoretically. Using the recursive Green's function
technique, we found the formation of a pi-junction in such systems. Moreover
the 0-pi phase transition is induced by increasing the temperature. Such
ferromagnetic-oxide based Josephson junctions may become an element in the
architecture of future quantum computers.Comment: 4 pages, 3 figure
Effect of d-f hybridization on the Josephson current through Eu-chalcogenides
A superconducting ring with a pi junction made from
superconductor/ferromagnetic-metal/superconductor (S-FM-S) exhibits a
spontaneous current without an external magnetic field in the ground state.
Such pi ring provides so-called quiet qubit that can be efficiently decoupled
from the fluctuation of the external field. However, the usage of the FM gives
rise to strong Ohmic dissipation. Therefore, the realization of pi junctions
without FM is expected for qubit applications. We theoretically consider the
possibility of the pi coupling for S/Eu-chalcogenides/S junctions based on the
d-f Hamiltonian. By use of the Green's function method we found that pi
junction can be formed in the case of the finite d-f hybridization between the
conduction d and the localized f electrons.Comment: 4 pages, 4 figure
Tunneling Hamiltonian description of the atomic-scale 0-pi transition in superconductor/ferromagnetic-insulator junctions
We show a perturbation theory of the Josephson transport through
ferromagnetic insulators (FIs). Recently we have found that the appearance of
the atomic scale 0-pi transition in such junctions based on numerical
calculations. In order to explore the mechanism of this anomalous transition,
we have analytically calculated the Josephson current using the tunneling
Hamiltonian theory and found that the spin dependent pi-phase shift in the FI
barrier gives the atomic scale 0-pi transition.Comment: 4 pages, 1 figure, to appear in Physica
with a production
The cross section of
process with a complete set of tree diagrams, 232 diagrams in the unitary
gauge, was calculated at the energy range of = 340 - 500 GeV by
using GRACE system. A main contribution to the cross section comes from
production, where and decay into and
, respectively. It was found that the
interference between the diagrams with production and those with
single- through pair production amounts to 10% at the
threshold energy region. In the energy region above twice of the top quark
mass, more than 95% of the cross section comes from the diagrams.Comment: 17 pages, 8 PostScript figures, LateX; To appear in Phys. Lett.
Possible observation of energy level quantization in an intrinsic Josephson junction
Energy level quantization (ELQ) is studied to clarify the macroscopic quantum
dynamics of the d-wave Josephson junction (JJ). The influences of the nodal
quasiparticles of d-wave superconductivity on the damping effect are
numerically evaluated on the basis of a phenomenological model. The
calculation, based on realistic parameters for a Bi2Sr2CaCu2O8+d (Bi2212)
intrinsic JJ, shows that the observation of ELQ is possible when the sweep rate
of the bias current exceeds 10 A/sec. High-sweep- rate measurements (121A/sec)
performed on a Bi2212 intrinsic JJ result in the appearance of multiple peaks
in the switching current distribution suggesting the realization of ELQ in the
d-wave JJ.Comment: 5 pages, 3 figure
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