We analyse the thermally activated depinning of an elastic string (line tension $\epsilon$) governed by Hall dynamics from a columnar defect modelled as a cylindrical potential well of depth $V_{ 0}$ for the case of a small external force $F.$ An effective 1D field Hamiltonian is derived in order to describe the 2D string motion. At high temperatures the decay rate is proportional to $F^{ { 5}/{ 2}}T^{ -{ 1}/{ 2}} \exp{ \left [{ F_{ 0}}/{ F}-{ U(F)}/{ T}\right ]},$ with $F_{ 0}$ a constant of order of the critical force and $U(F) \sim{ \left ({ \epsilon V_{ 0}})}^{ { 1}/{ 2}}{ V_{ 0}/{ F}}$ the activation energy. The results are applied to vortices pinned by columnar defects in superclean superconductors.
Categories: cond-mat.supr-con