Energy gap from tunneling and metallic contacts onto MgB2: Possible evidence for a weakened surface layer - art. no. 220504

Authors
Schmidt, H Zasadzinski, JF Gray, KE Hinks, DG
Citation
H. Schmidt et al., Energy gap from tunneling and metallic contacts onto MgB2: Possible evidence for a weakened surface layer - art. no. 220504, PHYS REV B, 6322(22), 2001, pp. 0504
Citations number
23
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
PHYSICAL REVIEW B
ISSN journal
01631829 → ACNP
Volume
6322
Issue
22
Year of publication
2001
Database
ISI
SICI code
0163-1829(20010601)6322:22<0504:EGFTAM>2.0.ZU;2-3
Abstract
Point-contact tunnel junctions using a Au tip on sintered MgB2 pellets reve al a sharp superconducting energy gap that is confirmed by subsequent metal lic contacts made on the same sample. The peak in the tunneling conductance and the metallic contact conductance follow the BCS form, but the gap valu es of 4.3 -4.6 meV are less than the weak-coupling BCS value of 5.9 meV for the bulk T-c of 39 K. The low value of Delta compared to the BCS value for the bulk T-c is possibly due to chemical reactions at the surface.