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$^{75}$As NMR of Ba(Fe$_{0.93}$Co$_{0.07}$)$_{2}$As$_{2}$ in High Magnetic Field

Authors :
Oh, Sangwon
Mounce, A. M.
Mukhopadhyay, S.
Halperin, W. P.
Vorontsov, A. B.
Bud'ko, S. L.
Canfield, P. C.
Furukawa, Y.
Reyes, A. P.
Kuhns, P. L.
Source :
Phys. Rev. B 83, 214501 (2011)
Publication Year :
2011

Abstract

The superconducting state of an optimally doped single crystal of Ba(Fe$_{0.93}$Co$_{0.07}$)$_2$As$_2$ was investigated by $^{75}$As NMR in high magnetic fields from 6.4 T to 28 T. It was found that the Knight shift is least affected by vortex supercurrents in high magnetic fields, $H>11$ T, revealing slow, possibly higher order than linear, increase with temperature at $T \lesssim 0.5 \, T_c$, with $T_c \approx 23 \, K$. This is consistent with the extended s-wave state with $A_{1g}$ symmetry but the precise details of the gap structure are harder to resolve. Measurements of the NMR spin-spin relaxation time, $T_2$, indicate a strong indirect exchange interaction at all temperatures. Below the superconducting transition temperature vortex dynamics lead to an anomalous dip in $T_2$ at the vortex freezing transition from which we obtain the vortex phase diagram up to $H = 28$ T.<br />Comment: 13 pages, 9 figures

Details

Database :
arXiv
Journal :
Phys. Rev. B 83, 214501 (2011)
Publication Type :
Report
Accession number :
edsarx.1101.1021
Document Type :
Working Paper
Full Text :
https://doi.org/10.1103/PhysRevB.83.214501