Energy gap from tunneling and metallic contacts onto MgB2: Possible evidence for a weakened surface layer
Abstract
Point-contact tunnel junctions using a Au tip on sintered MgB2 pellets reveal a sharp superconducting energy gap that is confirmed by subsequent metallic contacts made on the same sample. The peak in the tunneling conductance and the metallic contact conductance follow the BCS form, but the gap values of 4.3-4.6 meV are less than the weak-coupling BCS value of 5.9 meV for the bulk Tc of 39 K. The low value of Δ compared to the BCS value for the bulk Tc is possibly due to chemical reactions at the surface.
- Publication:
-
Physical Review B
- Pub Date:
- June 2001
- DOI:
- 10.1103/PhysRevB.63.220504
- arXiv:
- arXiv:cond-mat/0102389
- Bibcode:
- 2001PhRvB..63v0504S
- Keywords:
-
- 75.30.Vn;
- 75.30.Et;
- 75.60.-d;
- Exchange and superexchange interactions;
- Domain effects magnetization curves and hysteresis;
- Condensed Matter - Superconductivity
- E-Print:
- 3 pages, 3 figures