Phys. Rev. Lett. 88, 047002 (2002) [4 pages]Exponential Temperature Dependence of the Penetration Depth in Single Crystal MgB2Received 8 June 2001; revised 7 August 2001; published 9 January 2002 The temperature dependence of the London penetration depth, λ(T), was measured in both single crystal and polycrystalline MgB2 samples by a high-resolution, radio frequency technique. A clear exponential temperature dependence of λ(T) was observed at low temperature, indicating s-wave pairing. A BCS fit to the lowest temperature data gives an in-plane energy gap Δ of 30±2K (2Δ/Tc = 1.5±0.1), which is significantly smaller than the standard BCS weak coupling value of 3.5. We find that the data are best described by a two-gap model. © 2002 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.88.047002
DOI:
10.1103/PhysRevLett.88.047002
PACS:
74.25.Nf
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