Non-exponential London penetration depth in RFeAsO$_{0.9}$F$_{0.1}$ (R=La,Nd) single crystals

C. Martin; M. E. Tillman; H. Kim; M. A. Tanatar; S. K. Kim; A. Kreyssig; R. T. Gordon; M. D. Vannette; S. Nandi; V. G. Kogan; S. L. Bud'ko; P. C. Canfield; A. I. Goldman; R. Prozorov

doi:10.1103/physrevlett.102.247002

arXiv · 0903.2220

Non-exponential London penetration depth in RFeAsO$_{0.9}$F$_{0.1}$ (R=La,Nd) single crystals

C. Martin·M. E. Tillman·H. Kim·M. A. Tanatar·S. K. Kim·A. Kreyssig·R. T. Gordon·M. D. Vannette·S. Nandi·V. G. Kogan·S. L. Bud'ko·P. C. Canfield·A. I. Goldman·R. Prozorov

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Abstract

The superconducting penetration depth, $\lambda(T)$, has been measured in RFeAsO$_{0.9}$F$_{0.1}$ (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, $\Delta \lambda_L(T)\propto T^{2}$ at low temperatures. The same $T^2$ variation of $\lambda(T)$ was found in non-magnetic 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 BaFe$_2$As$_2$ (122) families of pnictide superconductors exhibit unconventional two-gap superconductivity.

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C. Martin, M. E. Tillman, H. Kim, M. A. Tanatar, S. K. Kim, A. Kreyssig, R. T. Gordon, M. D. Vannette, S. Nandi, V. G. Kogan, S. L. Bud'ko, P. C. Canfield, A. I. Goldman, R. Prozorov. 2009-03-12. Non-exponential London penetration depth in RFeAsO$_{0.9}$F$_{0.1}$ (R=La,Nd) single crystals. https://doi.org/10.1103/physrevlett.102.247002

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