Issue
EPL
Volume 84, Number 4, November 2008
Article Number 47004
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/84/47004
Published online 10 November 2008
EPL, 84 (2008) 47004
DOI: 10.1209/0295-5075/84/47004

Tc-dependence of energy gap and asymmetry of coherence peaks in NdBa2Cu3O7-$_\delta$ superconductors

P. Das1, M. R. Koblischka1, Th. Wolf2, P. Adelmann2 and U. Hartmann1

1   Institute of Experimental Physics, University of Saarland - D-66041 Saarbruecken, Germany, EU
2   Institute of Solid State Physics, Forschungzentrum Karlsruhe - D-76021 Karlsruhe, Germany, EU


received 14 August 2008; accepted in final form 13 October 2008; published November 2008
published online 10 November 2008

Abstract
We report here the results of scanning tunneling spectroscopy experiments performed on hole-doped NdBa2Cu3O7-$_\delta$ single crystals of Tc values of 76 K, 93.5 K and 95.5 K. The energy gaps are observed to be increasing with decreasing Tc values. The coherence peaks are asymmetric with the peaks at the filled states being larger than those at the empty ones. The asymmetry increases with decreasing Tc. The observed asymmetry and its Tc-dependence can be explained by considering the Mott insulating nature of the material at the undoped state.

PACS
74.72.Bk - Y-based cuprates.
74.25.Jb - Electronic structure.
74.50.+r - Tunneling phenomena; point contacts, weak links, Josephson effects.

© EPLA 2008