3,250 research outputs found
Magnetic field dependence of the critical current in stacked Josephson junctions. Evidence for fluxon modes in Bi2Sr2CaCu2O8+x mesas
Modulation of the critical current across layers, Ic(H), of stacked Josephson
junctions (SJJs) as a function of an applied magnetic field parallel to the
junction planes is studied theoretically and experimentally for different
junction lengths and coupling parameters. It is shown that the Ic(H) patterns
of long SJJs are very complicated without periodicity in H. This is due to
interaction between junctions in the stack. This, in turn, gives rise to the
existence of multiple quasi-equilibrium Josephson fluxon modes and submodes
which are different with respect to the symmetry of the phase and the fluxon
sequence in SJJs. The critical current of long SJJs is multiple valued and is
governed by switching between energetically close fluxon modes/submodes. Due to
this, the probability distribution of the critical current may become wide and
may consist of multiple maxima each representing a particular mode/submode.
Experimentally, multiple branched Ic(H) patterns and multiple maxima in the Ic
probability distribution were observed for Bi2Sr2CaCu2O8+x intrinsic SJJs,
which are in a good agreement with numerical simulations and support the idea
of having different quasi-equilibrium fluxon modes/submodes in intrinsic SJJs.Comment: 5 pages, 5 figure
3-junction SQUID rocking ratchet
We investigate 3-junction SQUIDs which show voltage rectification if biased
with an ac current drive with zero mean value. The Josephson phase across the
SQUID experiences an effective ratchet potential, and the device acts as an
efficient rocking ratchet, as demonstrated experimentally for adiabatic and
nonadiabatic drive frequencies. For high-frequency drives the rectified voltage
is quantized due to synchronization of the phase dynamics with the external
drive. The experimental data are in excellent agreement with numerical
simulations including thermal fluctuations.Comment: 5 pages, 4 figures -- Fig.4 revise
General Report for the Theme Three – Case Histories in Dams, Embankments and Slopes
Of the approximately forty papers submitted for sessions 3A and 3B on Case Histories in Dams, Embankments and Slopes, eighteen specifically discuss dams, foundations for dams or tailings dams. Table 1 presents a capsule summary of those papers that discuss dams and their foundations. Table 2 is a similar capsule summary of the five papers that discuss performance, design and/or construction of tailings dams or spoil piles. This general report summarizes and comments on the papers listed in Tables 1 and 2, presents several abbreviated case histories that parallel those presented in the papers, comments on several points not covered in the various papers, and ends with a few concluding remarks
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