Upper critical field of Ba1- x K x BiO3 measured by magnetotunneling spectroscopy
Abstract
In contrast to the conventional picture the upper critical fields measured by magnetoresistance in high-Tc superconductors including cubic Ba1-xKxBiO3, reveal a positive curvature in the temperature dependence. Several explanations have been proposed, but in magnetoresistance measurements flux-flow phenomena can play a role. We address the problem by tunneling spectroscopy, where we measure the superconducting density of states. The elastic tunneling current has been measured in the whole temperature and magnetic-field range up to the critical values. The obtained Hc2(T) dependence is in agreement with the Werthamer-Helfand-Hohenberg prediction.
- Publication:
-
Journal of Low Temperature Physics
- Pub Date:
- December 1996
- DOI:
- 10.1007/BF00753869
- Bibcode:
- 1996JLTP..105.1237S