The recent synthesis of the superconductor LaFeAsO0.89F0.11 with transition temperature Tc ≈ 26 K (refs 1–4) has been quickly followed by reports of even higher transition temperatures in related compounds: 41 K in CeFeAsO0.84F0.16 (ref. 5), 43 K in SmFeAsO0.9F0.1 (ref. 6), and 52 K in NdFeAsO0.89F0.11 and PrFeAsO0.89F0.11 (refs 7, 8). These discoveries have generated much interest9,10 in the mechanisms and manifestations of unconventional superconductivity in the family of doped quaternary layered oxypnictides LnOTMPn (Ln: La, Pr, Ce, Sm; TM: Mn, Fe, Co, Ni; Pn: P, As), because many features of these materials set them apart from other known superconductors. Here we report resistance measurements of LaFeAsO0.89F0.11 at high magnetic fields, up to 45 T, that show a remarkable enhancement of the upper critical field Bc2 compared to values expected from the slopes dBc2/dT ≈ 2 T K-1 near Tc, particularly at low temperatures where the deduced Bc2(0) ≈ 63–65 T exceeds the paramagnetic limit. We argue that oxypnictides represent a new class of high-field superconductors with Bc2 values surpassing those of Nb3Sn, MgB2 and the Chevrel phases, and perhaps exceeding the 100 T magnetic field benchmark of the high-Tc copper oxides.
Subscribe to Journal
Get full journal access for 1 year
only $3.83 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Kamihara, Y., Watanabe, T., Hirano, M. & Hosono, H. Iron-based layered superconductor La[O1-x F x ]FeAs (x = 0.05-0.12) with T c = 26 K. J. Am. Chem. Soc. 130, 3296–3297 (2008)
Zhu, X., Yang, H., Fang, L., Mu, G. & Wen, H.-H. Upper critical field, Hall effect and magnetoresistance in the iron-based layered superconductor LaO0. 9F0. 1-δFeAs. Preprint at 〈http://arxiv.org/abs/0803.1288v1〉 (2008)
Chen, G. F. et al. Superconducting properties of Fe-based layered superconductor LaO0. 9F0. 1-δ FeAs. Preprint at 〈http://arxiv.org/abs/0803.0128v1〉 (2008)
Sefat, A. S. et al. Electron correlations in the superconductor LaFeAsO0. 89F0. 11 with low carrier density. Phys. Rev. B 77 174503 (2008)
Chen, G. F. et al. Superconductivity at 41K and its competition with spin-density-wave instability in layered CeO1-xFx FeAs. Preprint at 〈http://arxiv.org/abs/0803.3790v2〉 (2008)
Chen, X. H. et al. Superconductivity at 43 K in samarium-arsenide oxides SmFeAsO1-xFx . Preprint at 〈http://arxiv.org/abs/0803.3603v1〉 (2008)
Ren, Z.-A. et al. Superconductivity in iron-based F-doped layered quaternary compound Nd[O1-xFx]FeAs. Preprint at 〈http://arxiv.org/abs/0803.4234〉 (2008)
Ren, Z.-A. et al. Superconductivity at 52K in iron-based F-doped layered quaternary compound Pr[O1-xFx]FeAs. Preprint at 〈http://arxiv.org/abs/0803.4283〉 (2008)
Zimmer, B. I., Jeitschko, W., Albering, J. H., Glaum, R. & Reehuis, M. The rare earth transition metal phosphide oxides LnFePO, LnRuPO and LnCoPO with ZrCuSiAs type structure. J. Alloy. Comp. 229, 238–242 (1995)
Quebe, P., Terbuchte, L. J. & Jeitschko, W. Quaternary rare earth transition metal arsenide oxides RTAsO (T = Fe, Ru, Co) with ZrCuSiAs type structure. J. Alloy. Comp. 302, 70–74 (2000)
Singh, D. J. & Du, M. H. LaFeAsO1-xFx: A low carrier density superconductor near itinerant magnetism. Preprint at 〈http://arxiv.org/abs/0803.0429v1〉 (2008)
Mazin, I. I., Singh, D. H., Johannes, M. D. & Du, M. H. Unconventional sign-reversal superconductivity in LaFeAsO1-xFx . Preprint at 〈http://arxiv.org/abs/0803.2740v1〉 (2008)
Cao, C., Hirschfeld, P. J. & Cheng, H.-P. Coexistence of antiferromagnetism with superconductivity in LaO1-xFxFeAs: effective Hamiltonian from ab initio studies. Preprint at 〈http://arxiv.org/abs/0803.3236〉 (2008)
Dai, X., Fang, Z., Zhou, Y. & Zhang, F. Even parity, orbital singlet and spin triplet pairing for superconducting La(O1-xFx)FeAs. Preprint at 〈http://arxiv.org/abs/0803.3982v1〉 (2008)
Dong, J. et al. Competing orders and spin-density wave instability in La(O1-xFx)FeAs. Preprint at 〈http://arxiv.org/abs/0803.3426v1〉 (2008)
Ma, F. & Lu, Z.-Y. Iron-based superconductor LaO1-xFxFeAs superconductor: an antiferromagnetic semimetal. Preprint at 〈http://arxiv.org/abs/0803.3286v1〉 (2008)
McGuire, M. A. et al. Evidence for the spin density wave in LaFeAsO. Preprint at 〈http://arxiv.org/abs/0804.0796〉 (2008)
Kuroki, K. et al. Unconventional superconductivity originating from disconnected Fermi surfaces in LaO1-xFxFeAs. Preprint at 〈http://arxiv.org/abs/0803.3325v1〉 (2008)
Lebegue, S. Electronic structure and properties of the Fermi surface of the superconductor LaOFeP. Phys. Rev. B 75, 035110 (2007)
Nagamatsu, J., Nakagawa, N., Muranaka, T., Zenitani, Y. & Akimitsu, J. Superconductivity at 39 K in magnesium diboride. Nature 410, 63–64 (2001)
Werthamer, N. R., Helfand, E. & Hohenberg, P. C. Temperature and purity dependence of the superconducting critical field, H c 2. III. Electron spin and spin-orbit effects. Phys. Rev. 147, 295–302 (1966)
Gurevich, A. Limits of the upper critical field in dirty two-gap superconductors. Physica C 456, 160–169 (2007); Enhancement of the upper critical field by nonmagnetic impurities in dirty two-gap superconductors. Phys. Rev. B 67, 184515 (2003)
Glazman, L. I., Koshelev, A. I. & Lebed’, A. G. Resistive transition and critical fields of superconducting ceramics. Sov. Phys. JETP 67, 1235–1241 (1988)
Blatter, G. & Geshkenbein, V. in The Physics of Superconductors Vol. 1 (eds Bennerman, K. H. & Ketterson, J. B.) 800 (Springer, Berlin, 2003)
Ahilan, K. et al. 19F NMR investigation of LaAsFeO0. 89F0. 11 superconductor. Preprint at 〈http://arxiv.org/abs/0804.4026〉 (2008)
Work at the NHMFL was supported by IHRP under NSF Cooperative Agreement, by the State of Florida, by the DOE, by the NSF Focused Research Group on Magnesium Diboride (FRG), and by AFOSR. Work at ORNL was supported by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences. We are grateful for discussions with G. Boebinger, E. Hellstrom, P. Lee, J. Jiang, and C. Tarantini at the NHMFL.
About this article
Cite this article
Hunte, F., Jaroszynski, J., Gurevich, A. et al. Two-band superconductivity in LaFeAsO0.89F0.11 at very high magnetic fields. Nature 453, 903–905 (2008) doi:10.1038/nature07058
Physica E: Low-dimensional Systems and Nanostructures (2020)
Critical-field slope reduction and upward curvature of the phase-transition lines of thin disordered superconducting YBa2Cu3O7−x films in strong magnetic fields
Physica C: Superconductivity and its Applications (2020)
Materials Research Express (2020)
Science China Physics, Mechanics & Astronomy (2020)
Annalen der Physik (2020)