NMR relaxation rate in superconducting pnictides: extended $s_{\pm }$ scenario

Abstract

Recently, several measurements of the nuclear spin lattice relaxation rate $T_1^{-1}$ in the newly discovered superconducting Fe-pnictides have been reported. These measurements generally show no coherence peak below $T_c$ and indicate a low temperature power law behavior, the characteristics commonly taken as evidence of unconventional superconductivity with lines of nodes crossing the Fermi surface. In this work we show that (i) the lack of a coherence peak is fully consistent with the previously proposed nodeless extended $s_{\pm }$-wave symmetry of the order parameter (whether in the clean or dirty limit) and (ii) the low temperature power law behavior can be also explained in the framework of the same model, but requires going beyond the Born model.

5 pages, 4 figures (We have dropped the oversimplified Dynes' model for the unitary limit. Rather, we now treat the Born, unitary, and intermediate regimes on the same footing)

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• Neutron and ARPES Constraints on the Couplings of the Multiorbital Hubbard Model for the Pnictides
• Spin Fluctuation Dynamics and Multiband Superconductivity in Iron Pnictides
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• Magnetic and Metallic State at Intermediate Hubbard U Coupling in Multiorbital Models for Undoped Fe Pnictides
• Detection of an Unconventional Superconducting Phase in the Vicinity of the Strong First-Order Magnetic Transition in CrAs Using ^75As-Nuclear Quadrupole Resonance
• Impurity-induced in-gap state and Tc in sign-reversing s-wave superconductors: analysis of iron oxypnictide superconductors
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• Experimental Detection of Sign-Reversal Pairing in Iron-Based Superconductors
• Development of very high Jc in Ba(Fe1-xCox)2As2 thin films grown on CaF2
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• 75As-NMR studies on La FeAsO1-xFx (x=0.14) under a pressure of 3GPa
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• Thermodynamics of $s_{\pm }-to-s_{++}$ transition in iron pnictides in the vicinity of the Born limit
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• Robust $s_{\pm }$-wave superconductivity against multi-impurity in iron-based superconductors