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Figure 16. The current at which the IV curve is discontinuous is lowest at the peaks in the R0 diagram. Outside of this diagram the discontinuity disappears. This is at positive current, but the negative side is approximately the same.

A close-up on the discontinuities reveal another detail: at the current where the Hall voltage makes a negative jump the bias point of the I-Vx curve jumps to a lower current. Figure 17 shows a close-up of the I-Vx and I-Vy curves at B=1.48 mT. Note that, in contrast with figure 15, at this field the Hall voltage jumps negative first and then positive. In figure 15 the first jump was positive and the second negative. A positive jump in Vy is always associated with a positive jump in Vx. A negative jump in Vy is associated with a jump in the bias point to lower current. If you look closely at figure 15 you will see the small jump, but this time at a higher current than the large one. Generally on the left side of the R0 peaks the first jump in Vy is positive, but on the right side, at higher fields, the first jump is negative.


Figure 17. Magnifying the discontinuous part of the I-Vx and I-Vy curves reveals a small jump in the I-Vx curve at the current where Vy makes a negative jump. The magnetic field is 1.48 mT.

A Hall voltage, Vy, means that vortices are have a velocity component parallel to the direction of the current. The jumps in Vy means a sudden change in the Hall angle, defined as arctan(Vy/Vx). The I-Vx curve indicate a suppression of the critical current at the junctions closest to the bars. Perhaps injection of vortices at the end of the bars when this critical current is exceeded can explain the Hall voltage.

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