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APS » Journals » Phys. Rev. Lett. » Volume 102 » Issue 12
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Phys. Rev. Lett. 102, 127004 (2009) [4 pages]

Unconventional London Penetration Depth in Single-Crystal Ba(Fe0.93Co0.07)2As2 Superconductors

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R. T. Gordon, N. Ni, C. Martin, M. A. Tanatar, M. D. Vannette, H. Kim, G. D. Samolyuk, J. Schmalian, S. Nandi, A. Kreyssig, A. I. Goldman, J. Q. Yan, S. L. Bud’ko, P. C. Canfield, and R. Prozorov*
Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA

Received 13 October 2008; published 26 March 2009

The London penetration depth λ(T) has been measured in single crystals of Ba(Fe0.93Co0.07)2As2. The observed low-temperature variation of λ(T) follows a power law, Δλ(T)∼Tn with n≈2.4±0.1, indicating the existence of normal quasiparticles down to at least 0.02Tc. This is in contrast with previous penetration depth measurements on single crystals of NdFeAsO1-xFx and SmFeAsO1-xFx, which indicate an anisotropic but nodeless gap. We discuss possible explanations of the observed power law behavior.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.102.127004
DOI:
10.1103/PhysRevLett.102.127004
PACS:
74.25.Nf, 74.20.Mn, 74.20.Rp

*Corresponding author.

prozorov@ameslab.gov

 
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