Enhancement Of Penetration Field In Vortex Matter In Mesoscopic Superconductors Due To Andreev Bound States

We study the field for the penetration of a first vortex, H-P, for vortex matter nucleated in micron-sized samples with edges aligned along the nodal and antinodal directions of the d-wave superconducting order parameter of Bi2Sr2CaCu2O8-delta. Here we present evidence that the H-P for vortex matter nucleated in mesoscopic samples with edges parallel to the nodal direction is larger than for the antinodal case, similar to 72% at low temperatures. This finding supports the theoretical proposal that surface Andreev bound states appearing in a sample with edges parallel to the nodal direction would produce an anomalous Meissner current that increases the Bean-Livingston barrier for vortex penetration.