Enhancement of the field of first flux penetration due to Andreev bound states in Bi_2Sr_2CaCu_2O_8+delta

Contributed Paper to be published in the Proceedings of the 9th International Conference on Materials and Mechanisms of Superconductivity, September 6th-12th, 2009, Tokyo, Japan.First flux penetration into single crystalline Bi_2Sr_2CaCu_2O_8+delta is investigated using magneto-optical imaging and Hall probe array magnetometry. Below 50 K, a slight enhancement of the field of first flux penetration, H_p, is found when the edge normals are oriented at 45° with respect to the principal (ab) crystal axes, rather than parallel to them. We discuss this effect in terms of a role of Andreev bound states [C. Iniotakis, T. Dahm, and N. Schopohl, Phys. Rev. Lett. 100, 037002 (2008).