15 research outputs found
Normal state properties of high angle grain boundaries in (Y,Ca)Ba2Cu3O7-delta
By lithographically fabricating an optimised Wheatstone bridge geometry, we
have been able to make accurate measurements of the resistance of grain
boundaries in Y1-xCaxBa2Cu3O7-d between the superconducting transition
temperature, Tc, and room temperature. Below Tc the normal state properties
were assessed by applying sufficiently high currents. The behaviour of the
grain boundary resistance versus temperature and of the conductance versus
voltage are discussed in the framework charge transport through a tunnel
barrier. The influence of misorientation angle, oxygen content, and calcium
doping on the normal state properties is related to changes of the height and
shape of the grain boundary potential barrier.Comment: 17 pages, 1 table, 5 figures, submitted to PR
The Normal State Resistivity of Grain Boundaries in YBa2Cu3O7-delta
Using an optimized bridge geometry we have been able to make accurate
measurements of the properties of YBa2Cu3O7-delta grain boundaries above Tc.
The results show a strong dependence of the change of resistance with
temperature on grain boundary angle. Analysis of our results in the context of
band-bending allows us to estimate the height of the potential barrier present
at the grain boundary interface.Comment: 11 pages, 3 figure
Mobile kinks and half-integer zero-field-like steps in highly discrete alternating Josephson junction arrays
The dynamics of a one-dimensional, highly discrete, linear array of
alternating and Josephson junctions is studied numerically, under
constant bias current at zero magnetic field. The calculated current - voltage
characteristics exhibit half-integer and integer zero-field-like steps for even
and odd total number of junctions, respectively. Inspection of the
instantaneous phases reveals that, in the former case, single kink
excitations (discrete semi-fluxons) are supported, whose propagation in the
array gives rise to the step, while in the latter case, a pair of
kink -- antikink appears, whose propagation gives rise to the
step. When additional kinks are inserted in the array, they are
subjected to fractionalization, transforming themselves into two closely spaced
kinks. As they propagate in the array along with the single kink or
the kink - antikink pair, they give rise to higher half-integer or
integer zero-field-like steps, respectively.Comment: 7 pages, 8 figures, submitted to Supercond. Sci. Techno