Volume 83, Number 3, August 2008
Article Number 37003
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 08 July 2008
EPL, 83 (2008) 37003
DOI: 10.1209/0295-5075/83/37003

Competition of multiband superconducting and magnetic order in ErNi2B2C observed by Andreev reflection

N. L. Bobrov1, V. N. Chernobay1, Yu. G. Naidyuk1, L. V. Tyutrina1, D. G. Naugle2, K. D. D. Rathnayaka2, S. L. Bud'ko3, P. C. Canfield3 and I. K. Yanson1

1  B. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine 47 Lenin Ave., 61103, Kharkiv, Ukraine
2  Department of Physics, Texas A&M University - College Station, TX 77843-4242, USA
3  Ames Laboratory, Department of Physics and Astronomy, Iowa State University - Ames, IA 50011, USA

received 6 March 2008; accepted in final form 6 June 2008; published August 2008
published online 8 July 2008

Point contacts (PC) Andreev reflection dV/dI spectra for the antiferromagnetic ($T_{\rm N}\simeq$ 6 K) superconductor ($T_{\rm c}\simeq$ 11 K) ErNi2B2C have been measured for the two main crystallographic directions. The observed retention of the Andreev reflection minima in dV/dI up to $T_{\rm c}$ directly points to an unusual superconducting order parameter (OP) vanishing at $T_{\rm c}$. The temperature dependence of the OP was obtained from dV/dI using the recent theory of Andreev reflection including the pair-breaking effect. For the first time the existence of two superconducting OPs in ErNi2B2C is shown. A distinct decrease of both OPs as temperature is lowered below $T_{\rm N}$ is observed.

74.45.+c - Proximity effects; Andreev effect; SN and SNS junctions.
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