1,050 research outputs found
Vortex-flow electromagnetic emission in stacked intrinsic Josephson junctions
We confirmed the existence of the collective transverse plasma modes excited
by the motion of the Josephson vortex lattice in stacked intrinsic Josephson
junctions of BiSrCaCuO by observing the multiple
subbranches in the Josephson-vortex-flow current-voltage characteristics. We
also observed the symptom of the microwave emission from the resonance between
the Josephson vortex lattice and the collective transverse plasma modes, which
provides the possibility of developing Josephson-vortex-flow electromagnetic
oscillators.Comment: 4 pages, 3 figure
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
Heating-compensated constant-temperature tunneling measurements on stacks of BiSrCaCuO intrinsic junctions
In highly anisotropic layered cuprates such as BiSrCaCuO
tunneling measurements on a stack of intrinsic junctions in a high-bias range
are often susceptible to self-heating. In this study we monitored the
temperature variation of a stack ("sample stack") of intrinsic junctions by
measuring the resistance change of a nearby stack ("thermometer stack") of
intrinsic junctions, which was strongly thermal-coupled to the sample stack
through a common Au electrode. We then adopted a
proportional-integral-derivative scheme incorporated with a substrate-holder
heater to compensate the temperature variation. This in-situ temperature
monitoring and controlling technique allows one to get rid of spurious
tunneling effects arising from the self-heating in a high bias range.Comment: 3 pages, 3 figure
Josephson-vortex-flow terahertz emission in layered high- superconducting single crystals
We report on the successful terahertz emission (0.61 THz) that is
continuous and tunable in its frequency and power, by driving Josephson
vortices in resonance with the collective standing Josephson plasma modes
excited in stacked BiSrCaCuO intrinsic Josephson junctions.
Shapiro-step detection was employed to confirm the terahertz-wave emission. Our
results provide a strong feasibility of developing long-sought solid-state
terahertz-wave emission devices
A Dynamic Information-Based Parking Guidance for Megacities considering Both Public and Private Parking
The constantly increasing number of cars in the megacities is causing severe parking problems. To resolve this problem, many cities adopt parking guidance system as a part of intelligent transportation system (ITS). However, the current parking guidance system stays in its infant stage since the obtainable information is limited. To enhance parking management in the megacity and to provide better parking guidance to drivers, this study introduces an intelligent parking guidance system and proposes a new methodology to operate it. The introduced system considers both public parking and private parking so that it is designed to maximize the use of spatial resources of the city. The proposed methodology is based on the dynamic information related parking in the city and suggests the best parking space to each driver. To do this, two kinds of utility functions which assess parking spaces are developed. Using the proposed methodology, different types of parking management policies are tested through the simulation. According to the experimental test, it is shown that the centrally managed parking guidance can give better results than individually preferred parking guidance. The simulation test proves that both a driver???s benefits and parking management of a city from various points of view can be improved by using the proposed methodology
Collective resonance modes of Josephson vortices in sandwiched stack of BiSrCaCuO intrinsic Josephson junctions
We observed splitting of the low-bias vortex-flow branch in a
dense-Josephson-vortex state into multiple sub-branches in current-voltage
characteristics of intrinsic Josephson junctions (IJJs) of
BiSrCaCuO single crystals in the long-junction limit.
Each sub-branch corresponds to a plasma mode in serially coupled Josephson
junctions. Splitting into low-bias linear sub-branches with a spread in the
slopes and the inter-sub-branch mode-switching character are in good
quantitative agreement with the prediction of the weak but finite
inter-junction capacitive-coupling model incorporated with the inductive
coupling. This suggests the importance of the role of the capacitive coupling
in accurately describing the vortex dynamics in serially stacked IJJs.Comment: 4 pages, 3 figures, 1 tabl
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