As75 NMR of Ba(Fe0.93Co0.07)2As2 in high magnetic field

Sangwon Oh, A. M. Mounce, S. Mukhopadhyay, W. P. Halperin, A. B. Vorontsov, S. L. Bud’ko, P. C. Canfield, Y. Furukawa, A. P. Reyes, and P. L. Kuhns
Phys. Rev. B 83, 214501 – Published 1 June 2011


The superconducting state of an optimally doped single crystal of Ba(Fe0.93Co0.07)2As2 was investigated by As75 NMR in high magnetic fields from 6.4 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 T0.5Tc, with Tc23 K. This is consistent with the extended s-wave state with A1g symmetry, but the precise details of the gap structure are harder to resolve. Measurements of the NMR spin-spin relaxation time T2 indicate a strong indirect exchange interaction at all temperatures. Below the superconducting transition temperature, abrupt changes in vortex dynamics lead to an anomalous dip in T2, consistent with vortex freezing from which we obtain the vortex phase diagram up to H=28 T.

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  • Received 1 January 2011


©2011 American Physical Society

Authors & Affiliations

Sangwon Oh1, A. M. Mounce1, S. Mukhopadhyay1, W. P. Halperin1, A. B. Vorontsov2, S. L. Bud’ko3, P. C. Canfield3, Y. Furukawa3, A. P. Reyes4, and P. L. Kuhns4

  • 1Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
  • 2Department of Physics, Montana State University, Bozeman, Montana 59717, USA
  • 3Ames Laboratory US DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
  • 4National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA

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Vol. 83, Iss. 21 — 1 June 2011

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