565 research outputs found
Collective Josephson vortex dynamics in a finite number of intrinsic Josephson junctions
We report the experimental confirmation of the collective transverse plasma
modes excited by the Josephson vortex lattice in stacks of intrinsic Josephson
junctions in BiSrCaCuO single crystals. The
excitation was confirmed by analyzing the temperature () and magnetic field
() dependencies of the multiple sub-branches in the Josephson-vortex-flow
region of the current-voltage characteristics of the system. In the near-static
Josephson vortex state for a low tunneling bias current, pronounced
magnetoresistance oscillations were observed, which represented a
triangular-lattice vortex configuration along the c axis. In the dynamic vortex
state in a sufficiently high magnetic field and for a high bias current,
splitting of a single Josephson vortex-flow branch into multiple sub-branches
was observed. Detailed examination of the sub-branches for varying field
reveals that sub-branches represent the different modes of the Josephson-vortex
lattice along the c axis, with varied configuration from a triangular to a
rectangular lattices. These multiple sub-branches merge to a single curve at a
characteristic temperature, above which no dynamical structural transitions of
the Josephson vortex lattice is expected
Phase dynamics of inductively coupled intrinsic Josephson junctions and terahertz electromagnetic radiation
The Josephson effects associated with quantum tunneling of Cooper pairs
manifest as nonlinear relations between the superconductivity phase difference
and the bias current and voltage. Many novel phenomena appear, such as Shapiro
steps in dc cuurent-voltage (IV) characteristics of a Josephson junction under
microwave shining, which can be used as a voltage standard. Inversely, the
Josephson effects provide a unique way to generate high-frequency
electromagnetic (EM) radiation by dc bias voltage. The discovery of cuprate
high-Tc superconductors accelerated the effort to develop novel source of EM
waves based on a stack of atomically dense-packed intrinsic Josephson junctions
(IJJs), since the large superconductivity gap covers the whole terahertz
frequency band. Very recently, strong and coherent terahertz radiations have
been successfully generated from a mesa structure of
single crystal which works both as the source
of energy gain and as the cavity for resonance. It is then found theoretically
that, due to huge inductive coupling of IJJs produced by the nanometer junction
separation and the large London penetration depth of order of of
the material, a novel dynamic state is stabilized in the coupled sine-Gordon
system, in which kinks in phase differences are developed responding
to the standing wave of Josephson plasma and are stacked alternatively in the
c-axis. This novel solution of the inductively coupled sine-Gordon equations
captures the important features of experimental observations. The theory
predicts an optimal radiation power larger than the one available to date by
orders of magnitude, and thus suggests the technological relevance of the
phenomena.Comment: review article (69 pages, 30 figures
From the Frenkel-Kontorova model to Josephson junction arrays - the Aubry's transition as a jamming-glass transition -
The Frenkel Kontorova (FK) model is known to exhibit the so called Aubry's
transition which is a jamming or frictional transition at zero temperature.
Recently we found similar transition at zero and finite temperatures in a
super-conducting Josephson junction array (JJA) on a square lattice under
external magnetic field. In the present paper we discuss how these problems are
related.Comment: 19 pages, 6 figures. To appear in the proceedings of YKIS2009
Frontiers in Nonequilibrium Physics, Progress in Theoretical Physics
supplement 2010
Submillimeter local oscillators for spaceborne heterodyne applications
Existing and prospective submillimeter local oscillator technologies are surveyed and compared with respect to criteria of suitability for application in spaceborne submillimeter heterodyne receivers as those proposed for the Large Deployable Reflector (LDR). Solid-state and plasma devices are considered in terms of fundamental limitations
Nature of the Low Field Transition in the Mixed State of High Temperature Superconductors
We have numerically studied the statics and dynamics of a model
three-dimensional vortex lattice at low magnetic fields. For the statics we use
a frustrated 3D XY model on a stacked triangular lattice. We model the dynamics
as a coupled network of overdamped resistively-shunted Josephson junctions with
Langevin noise. At low fields, there is a weakly first-order phase transition,
at which the vortex lattice melts into a line liquid. Phase coherence parallel
to the field persists until a sharp crossover, conceivably a phase transition,
near which develops at the same temperature as an infinite
vortex tangle. The calculated flux flow resistivity in various geometries near
closely resembles experiment. The local density of field induced
vortices increases sharply near , corresponding to the experimentally
observed magnetization jump. We discuss the nature of a possible transition or
crossover at (B) which is distinct from flux lattice melting.Comment: Updated references. 46 pages including low quality 25 eps figures.
Contact [email protected] or visit
http://www.physics.ohio-state.edu:80/~ryu/ for better figures and additional
movie files from simulations. To be published in Physical Review B1 01Jun9
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