Two-band superconductivity in LaFeAsO0.89F0.11 at very high magnetic fields.
Frank Hunte,Jan Jaroszynski,Alex Gurevich,David C. Larbalestier,Rongying Jin,Athena S. Sefat,Michael A. McGuire,Brian C. Sales,David K. Christen,David Mandrus +9 more
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In this article, the authors report very high-field resistance measurements of LaFeAsO0.89F0.11 up to 45 T, which show a remarkable enhancement of the upper critical field Bc2 as compared to values expected from the slopes dBc2/dT ≈ 2 T/K near Tc, particularly at low temperatures where the deduced Bc 2(0) ≈ 63-65 T exceeds the paramagnetic limit.Abstract:
The synthesis of the novel superconductor LaFeAsO0.89F0.11 with transition temperature Tc ∼ 26 K has been quickly followed by reports of even higher Tcs. These discoveries have generated much interest in the mechanisms and manifestations of unconventional superconductivity in the family of doped quaternary layered oxypnictides, because many features of these materials set them apart from other superconductors. Hunte et al. report very high-field resistance measurements of LaFeAsO0.89F0.11 up to 45 T, which show a remarkable enhancement of the upper critical field Bc2 as compared to values expected from the slopes dBc2/dT ≈ 2 T/K near Tc, particularly at low temperatures where the deduced Bc2(0) ≈ 63–65 T exceeds the paramagnetic limit. 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.read more
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LiFeAs: An intrinsic FeAs-based superconductor with Tc=18 K
Joshua Tapp,Zhongjia Tang,Bing Lv,Kalyan Sasmal,Bernd Lorenz,Paul C. W. Chu,Paul C. W. Chu,Paul C. W. Chu,Arnold M. Guloy +8 more
TL;DR: LiFeAs as mentioned in this paper is a high-T$ Fe-based superconducting stoichiometric compound, which exhibits superconductivity at ambient pressures without chemical doping and exhibits a respectable transition temperature with electron-like carriers and a very high critical field.
Journal ArticleDOI
Superconducting Fe-based compounds (A1-xSrx)Fe2As2 with A=K and Cs with transition temperatures up to 37 K.
Kalyan Sasmal,Bing Lv,Bernd Lorenz,Arnold M. Guloy,Feng Chen,Y.Y. Xue,Ching-Wu Chu,Ching-Wu Chu,Ching-Wu Chu +8 more
TL;DR: New high-T{c} Fe-based superconducting compounds, AFe2As2 with A=K, Cs, K/Sr, and Cs/SR, were synthesized, and their electronic and structural behavior demonstrate the crucial role of the (Fe2 as2) layers in the superconductivity of the Fe- based layered systems.
Journal ArticleDOI
To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report
TL;DR: In this paper, the authors present a summary of experimental reports on newly discovered iron-based superconductors as they were known at the end of 2008 and introduce experimental results that reveal basic physical properties in the normal and superconducting states.
Journal ArticleDOI
Nearly isotropic superconductivity in (Ba,K)Fe 2 As 2
Huiqiu Yuan,Huiqiu Yuan,John Singleton,Fedor Balakirev,S. A. Baily,G. F. Chen,J. L. Luo,Nan Wang +7 more
TL;DR: Measurements of the electrical resistivity in single crystals of (Ba,K)Fe2As2 in a magnetic field up to 60 T find that the superconducting properties are in fact quite isotropic, being rather independent of the direction of the applied magnetic fields at low temperature.
Journal ArticleDOI
To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report
TL;DR: In this paper, the authors present a summary of experimental reports on newly discovered iron-based superconductors as they were known at the end of 2008 and introduce experimental results that reveal basic physical properties in the normal and superconducting states.
References
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Iron-Based Layered Superconductor La[O1-xFx]FeAs (x = 0.05−0.12) with Tc = 26 K
TL;DR: It is reported that a layered iron-based compound LaOFeAs undergoes superconducting transition under doping with F- ions at the O2- site and exhibits a trapezoid shape dependence on the F- content.
Journal ArticleDOI
Superconductivity at 39 K in magnesium diboride
TL;DR: In this article, the authors reported the discovery of bulk superconductivity in magnesium diboride, MgB2, with a transition temperature of 39'K, which they believe to be the highest yet determined for a non-copper-oxide bulk superconductor.
Journal ArticleDOI
Temperature and Purity Dependence of the Superconducting Critical Field, H c 2 . III. Electron Spin and Spin-Orbit Effects
TL;DR: In this paper, a solution of the linearized Gor'kov equations for the upper critical magnetic field of a bulk type-II superconductor is extended to include the effects of Pauli spin paramagnetism and spin-orbit impurity scattering.
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Unconventional Superconductivity with a Sign Reversal in the Order Parameter of LaFeAsO 1-x F x
TL;DR: It is argued that the newly discovered superconductivity in a nearly magnetic, Fe-based layered compound is unconventional and mediated by antiferromagnetic spin fluctuations, though different from the usual superexchange and specific to this compound.
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Iron-Based Layered Superconductor: LaOFeP
Yoichi Kamihara,Hidenori Hiramatsu,Masahiro Hirano,Ryuto Kawamura,Hiroshi Yanagi,Toshio Kamiya,Hideo Hosono +6 more
TL;DR: Magnetic and electrical resistivity measurements verify the occurrence of the superconducting transition at approximately 4 K in an iron-based layered oxy-pnictide LaOFeP.