| Issue |
Europhys. Lett.
Volume 50, Number 5, June I 2000
|
|
|---|---|---|
| Page(s) | 663 - 667 | |
| Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
| DOI | https://doi.org/10.1209/epl/i2000-00321-x | |
| Published online | 01 September 2002 | |
Andreev reflections and tunneling spectroscopy
on underdoped 
Université Libre de Bruxelles, Service de Physique des Solides
CP233, Blvd du Triomphe, B-1050 Brussels, Belgium
Received:
17
January
2000
Accepted:
31
March
2000
Andreev-reflection and tunneling studies have been carried out
on a single crystal of underdoped 
(NCCO) by
using Ag, Pt-Ir and Nb tips to clarify the symmetry of its order parameter.
Surprisingly, we observed in the NCCO, on the one hand, the Josephson
current (with Nb tip) which indicates the presence of s-wave order
parameter, on the other hand, a zero-bias conductance peak (with Ag tip)
which is a manifestation of d-wave order parameter. In addition, we find
the presence of two distinct energy scales in the underdoped NCCO: the
smallest energy scale is associated with the Andreev gap and c-axis
tunneling gap, and the second scale corresponds to the maximum in-plane tunneling gap. It
seems that the phenomenon of superconductivity in electron- and hole-doped cuprates can be
understood within a common scheme.
PACS: 74.50.+r – Proximity effects, weak links, tunneling phenomena, and Josephson effects / 74.72.Jt – Other cuprates / 74.25.Dw – Superconductivity phase diagrams
© EDP Sciences, 2000
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