Issue
EPL
Volume 83, Number 5, September 2008
Article Number 57004
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/83/57004
Published online 27 August 2008
EPL, 83 (2008) 57004
DOI: 10.1209/0295-5075/83/57004

Point-contact spectroscopy of iron-based layered superconductor ${\rm LaO}_{0.9}{\rm F}_{0.1-\delta}{\rm FeAs}$

Lei Shan, Yonglei Wang, Xiyu Zhu, Gang Mu, Lei Fang, Cong Ren and Hai-Hu Wen

National Laboratory for Superconductivity, Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences - P.O. Box 603, Beijing 100190, China

lshan@aphy.iphy.ac.cn

received 12 May 2008; accepted in final form 17 July 2008; published September 2008
published online 27 August 2008

Abstract
We present point-contact spectroscopy data for junctions between a normal metal and the newly discovered F-doped superconductor ${\rm LaO}_{0.9}{\rm F}_{0.1-\delta}{\rm FeAs}$ (F-LaOFeAs). A zero-bias conductance peak was observed and its shape and magnitude suggest the presence of Andreev bound states at the surface of F-LaOFeAs, which provides a possible evidence of an unconventional pairing symmetry with a nodal gap function. The maximum gap value $\Delta _{0}$$\approx$ 3.9$\pm$0.7  meV was determined from the measured spectra, in good agreement with the recent experiments on specific heat and lower critical field.

PACS
74.20.Rp - Pairing symmetries (other than s-wave).
74.50.+r - Tunneling phenomena; point contacts, weak links, Josephson effects.
74.70.Dd - Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.).

© EPLA 2008