694 research outputs found
Alternating dynamic state in intrinsic Josephson-junction stacks self-generated by internal resonance
Intrinsic Josephson-junction stacks realized in high-temperature
superconductors provide a very attractive base for developing coherent sources
of electromagnetic radiation in the terahertz frequency range. A promising way
to synchronize phase oscillations in all the junctions is to excite an internal
cavity resonance. We demonstrate that this resonance promotes the formation of
an alternating coherent state, in which the system spontaneously splits into
two subsystems with different phase-oscillation patterns. There is a static
phase shift between the oscillations in the two subsystems which changes from 0
to in a narrow region near the stack center. The oscillating electric
and magnetic fields are almost homogeneous in all the junctions. The formation
of this state promotes efficient pumping of the energy into the cavity
resonance leading to strong resonance features in the current-voltage
dependence.Comment: 4 pages, 3 figure
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.
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