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Nonexponential London Penetration Depth of FeAs-Based Superconducting RFeAsO0.9F0.1 (R=La, Nd) Single Crystals

TitleNonexponential London Penetration Depth of FeAs-Based Superconducting RFeAsO0.9F0.1 (R=La, Nd) Single Crystals
Publication TypeJournal Article
Year of Publication2009
AuthorsMartin C, Tillman ME, Kim H, Tanatar MA, Kim SK, Kreyssig A, Gordon RT, Vannette MD, Nandi S, Kogan VG, Bud'ko SL, Canfield PC, Goldman AI, Prozorov R
Journal TitlePhysical Review Letters
Volume102
Pages247002
Date Published06/19
ISBN Number0031-9007
Accession NumberISI:000267197900056
Keywordsanisotropy, field, gaps, mgb2, smfeaso0.8f0.2
Abstract

The superconducting penetration depth lambda(T) has been measured in RFeAsO0.9F0.1 (R=La, Nd) single crystals (R-1111). In Nd-1111, we find an upturn in lambda(T) upon cooling and attribute it to the paramagnetism of the Nd ions, similar to the case of the electron-doped cuprate Nd-Ce-Cu-O. After the correction for paramagnetism, the London penetration depth variation is found to follow a power-law behavior, Delta lambda(L)(T)proportional to T-2 at low temperatures. The same T-2 variation of lambda(T) was found in nonmagnetic La-1111 crystals. Analysis of the superfluid density and of penetration depth anisotropy over the full temperature range is consistent with two-gap superconductivity. Based on this and on our previous work, we conclude that both the RFeAsO (1111) and BaFe2As2 (122) families of pnictide superconductors exhibit unconventional two-gap superconductivity.
URL<Go to ISI>://000267197900056
DOI10.1103/Physrevlett.102.247002