138,337 research outputs found
Magnetic oscillations of critical current in intrinsic Josephson-junction stacks
A key phenomenon related to the Josephson effect is oscillations of different
properties of superconducting tunneling junctions with magnetic field. We
consider magnetic oscillations of the critical current in stacks of intrinsic
Josephson junctions, which are realized in mesas fabricated from layered
high-temperature superconductors. The oscillation behavior is very different
from the case of a single junction. Depending on the stack lateral size,
oscillations may have either the period of half flux quantum per junction
(wide-stack regime) or one flux quantum per junction (narrow-stack regime). We
study in detail the crossover between these two regimes. Typical size
separating the regimes is proportional to magnetic field meaning that the
crossover can be driven by the magnetic field. In the narrow-stack regime the
lattice structure experiences periodic series of phase transitions between
aligned rectangular configuration and triangular configuration. Triangular
configurations in this regime is realized only in narrow regions near
magnetic-field values corresponding to integer number of flux quanta per
junction.Comment: 17 pages, 11 figures, subm. Phys. Rev.
Jamming and percolation of parallel squares in single-cluster growth model
This work studies the jamming and percolation of parallel squares in a
single-cluster growth model. The Leath-Alexandrowicz method was used to grow a
cluster from an active seed site. The sites of a square lattice were occupied
by addition of the equal size squares (E-problem) or a mixture of
and () squares (M-problem). The larger
squares were assumed to be active (conductive) and the smaller squares were assumed to be blocked (non-conductive). For equal size
squares (E-problem) the value of was
obtained for the jamming concentration in the limit of .
This value was noticeably larger than that previously reported for a random
sequential adsorption model, . It was observed that the
value of percolation threshold (i.e., the ratio of the area of
active squares and the total area of squares in the
percolation point) increased with an increase of . For mixture of and squares (M-problem), the value of
noticeably increased with an increase of at a fixed value of and
approached 1 at . This reflects that percolation of larger
active squares in M-problem can be effectively suppressed in the presence of
smaller blocked squares.Comment: 11 pages, 9 figure
Diquark and triquark correlations in the deconfined phase of QCD
We use the non-perturbative Q\bar Q potential at finite temperatures derived
in the Field Correlator Method to obtain binding energies for the lowest
eigenstates in the Q\bar Q and QQQ systems (Q=c,b). The three--quark problem is
solved by the hyperspherical method. The solution provides an estimate of the
melting temperature and the radii for the different diquark and triquark bound
states. In particular we find that J/\psi and ground states survive up to
T \sim 1.3 T_c, where T_c is the critical temperature, while the corresponding
bottomonium states survive even up to higher temperature, T \sim 2.2 T_c.Comment: 11 pages, 1 figure; published versio
Hybridization and interference effects for localized superconducting states in strong magnetic field
Within the Ginzburg-Landau model we study the critical field and temperature
enhancement for crossing superconducting channels formed either along the
sample edges or domain walls in thin-film magnetically coupled superconducting
- ferromagnetic bilayers. The corresponding Cooper pair wave function can be
viewed as a hybridization of two order parameter (OP) modes propagating along
the boundaries and/or domain walls. Different momenta of hybridized OP modes
result in the formation of vortex chains outgoing from the crossing point of
these channels. Near this crossing point the wave functions of the modes merge
giving rise to the increase in the critical temperature for a localized
superconducting state. The origin of this critical temperature enhancement
caused by the wave function squeezing is illustrated for a limiting case of
approaching parallel boundaries and/or domain walls. Using both the variational
method and numerical simulations we have studied the critical temperature
dependence and OP structure vs the applied magnetic field and the angle between
the crossing channels.Comment: 12 pages, 13 figure
The study of amplitude and phase relaxation impact on the quality of quantum information technologies
The influence of amplitude and phase relaxation on evolution of quantum
states within the formalism of quantum operations is considered. The model of
polarizing qubits where noises are determined by the existence of spectral
degree of freedom that shows up during the light propagation inside anisotropic
mediums with dispersion is studied. Approximate analytic model for calculation
of phase plate impact on polarizing state with dispersion influence taken into
consideration is suggested.Comment: 7 pages, 4 figures, report for the International Symposium "Quantum
Informatics-2014" (QI-2014), Zvenigorod, Moscow region, October 06-10, 201
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