Magnetic field dependence of spin-lattice relaxation in the s ± state of Ba 0.67K 0.33Fe 2As 2

Sangwon Oh*, A. M. Mounce, W. P. Halperin, C. L. Zhang, Pengcheng Dai, A. P. Reyes, P. L. Kuhns

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The spatially averaged density of states N(0) of an unconventional d-wave superconductor is magnetic field dependent, proportional to H1 /2, owing to the Doppler shift of quasiparticle excitations in a background of vortex supercurrents. This phenomenon, called the Volovik effect, has been predicted to exist for a sign-changing s ± state, although it is absent in a single-band s-wave superconductor. Consequently, we expect there to be Doppler contributions to the NMR spin-lattice relaxation rate, 1/T 1∞N (0 )2, for an s ± state which will depend on the magnetic field. We have measured the 75As 1/T 1 in a high-quality single crystal of Ba 0.67K 0.33Fe 2As 2 over a wide range of field up to 28 T. Our spatially resolved measurements show that indeed there are Doppler contributions to 1/T 1 which increase closer to the vortex core, with a spatial average proportional to H2, inconsistent with recent theory.

Original languageEnglish (US)
Article number174508
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume85
Issue number17
DOIs
StatePublished - May 11 2012

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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