What is the best gate for vortex entry into type-II superconductor?

A theoretical description of the influence of surface irregularities (such as wedge-Eke cracks) on the Bean-Livingston energy barrier is presented. A careful quantitative estimate of the field of the first vortex entry H* int o a homogeneous bulk superconductor with crack-like defects is obtained, Th is estimate is based on an exact analytical solution for the Meissner curre nt distribution in a bulk superconductor with a single two-dimensional infi nitely thin crack. This thin crack is characterized by the lowest H* value and, thus, appears to be the best gate for vortex entry. (C) 2001 Elsevier Science B.V. All rights reserved.