Figure 3.

Vortices move only after contact with a stress-dependent effectiveness. (a) An approach curve measured via capacitive sensing of the sample plane (black dots). The contact point is reflected by the sharp change in the capacitance slope. (b) Scans at selected heights above and in contact with a single vortex, color coded to correspond to the set of points on the capacitance curve (a). The scan was carried out from left to right and then up to the next row. The vortex moved only after contact (positions 1 to 2) and again after repeated scans in contact (positions 2 to 3). (c) Horizontal cross sections taken at the center of the vortex imaged in b, color-coded to match the relevant points on the capacitance curve. The signal increased during approach, yet the vortex moved only after contact (at maximum signal). The shallow dip observed between positions 2 and 3 is a signal from another vortex (see panel b) that extends in the y-direction due to the keyhole shape of the SQUID (Supporting Information).