Thermal and quantum creep of vortices trapped by twin boundaries and columnar defects

We have analyzed the creep process in which a vortex loop is disconnecting from a twin boundary or a columnar defect and is then expanding, driven by a transport current. The shape of the vortex loop is in general an arc and not a semicircle. The contact angle α between the loop and the plane of the twin-boundary or the axis of the columnar defect is small if the trapping potential is small. The energy barrier resisting the vortex creep is strongly decreased as ${\mathrm{\alpha }}^3$ for small α. Quantum tunneling through this barrier is analyzed for a massless vortex motion governed by the Magnus force. The tunneling rate W is strongly enhanced for small contact angles with lnW∼${\mathrm{\alpha }}^5$.