The unzipping of vortex lines using magnetic-force microscopy from extended defects is studied theoretically. We study both the unzipping of an isolated vortex from common defects, such as columnar pins and twin planes, and the unzipping of a vortex from a plane in the presence of other vortices. We show, using analytic and numerical methods, that the universal properties of the unzipping transition of a single vortex depend only on the dimensionality of the defect in the presence and absence of disorder. The unzipping of a vortex from a plane populated with many vortices is shown to be very sensitive to the properties of the vortices in the two-dimensional plane. In particular, such unzipping experiments can be used to measure the “Luttinger-liquid parameter” of the vortices in the plane. In addition, we suggest a method for measuring the line tension of the vortex directly using the experiments.

• Received 19 June 2007

DOI:https://doi.org/10.1103/PhysRevB.76.144501