Evidence for Surface Andreev Bound States in Cuprate Superconductors from Penetration Depth Measurements
Tunneling and theoretical studies have suggested that Andreev bound states form at certain surfaces of unconventional superconductors. Through studies of the temperature and field dependence of the in-plane magnetic penetration depth λab at low temperature, we have found strong evidence for the presence of these states in clean single crystal YBCO and BSCCO. Crystals cut to expose (110) surfaces show a strong upturn in λab at around 7 K, when the field is oriented along the c axis. In YBCO this upturn is completely suppressed by a field of ~0.1 T.
Physical Review Letters
- Pub Date:
- February 2001
- Condensed Matter - Superconductivity;
- Condensed Matter - Strongly Correlated Electrons
- 4 pages 2 column revtex + 4 postscript figures. Submitted to PRL