Experimental elucidation of the origin of the ‘double spin resonances’ in Ba(Fe1xCox)2As2

Meng Wang, M. Yi, H. L. Sun, P. Valdivia, M. G. Kim, Z. J. Xu, T. Berlijn, A. D. Christianson, Songxue Chi, M. Hashimoto, D. H. Lu, X. D. Li, E. Bourret-Courchesne, Pengcheng Dai, D. H. Lee, T. A. Maier, and R. J. Birgeneau
Phys. Rev. B 93, 205149 – Published 26 May 2016

Abstract

We report a combined study of the spin resonances and superconducting gaps for underdoped (Tc=19 K), optimally doped (Tc=25 K), and overdoped (Tc=19 K) Ba(Fe1xCox)2As2 single crystals with inelastic neutron scattering and angle resolved photoemission spectroscopy. We find a quasi-two-dimensional spin resonance whose energy scales with the superconducting gap in all three compounds. In addition, anisotropic low energy spin excitation enhancements in the superconducting state have been deduced and characterized for the under and optimally doped compounds. Our data suggest that the quasi-two-dimensional spin resonance is a spin exciton that corresponds to the spin singlet-triplet excitations of the itinerant electrons. However, the intensity enhancements of the anisotropic spin excitations are dominated by the out-of-plane spin excitations of the ordered moments due to the suppression of damping in the superconducting state. Hence we offer an interpretation of the double energy scales differing from previous interpretations based on anisotropic superconducting energy gaps and systematically explain the doping-dependent trend across the phase diagram.

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  • Received 22 February 2016
  • Revised 29 March 2016

DOI:https://doi.org/10.1103/PhysRevB.93.205149

©2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Meng Wang1,*, M. Yi1,†, H. L. Sun2, P. Valdivia1, M. G. Kim3, Z. J. Xu1, T. Berlijn4, A. D. Christianson5, Songxue Chi5, M. Hashimoto6, D. H. Lu6, X. D. Li2, E. Bourret-Courchesne3, Pengcheng Dai7, D. H. Lee1,3, T. A. Maier4, and R. J. Birgeneau1,3,8

  • 1Department of Physics, University of California, Berkeley, California 94720, USA
  • 2Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Science, Beijing 100049, China
  • 3Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
  • 4Center for Nanophase Materials Sciences and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 5Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 6Stanford Synchrotron Radiation Lightsource, SLAS National Accelerator Laboratory, Menlo Park, California 94025, USA
  • 7Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
  • 8Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA

  • *wangm@berkeley.edu
  • mingyi@berkeley.edu

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Issue

Vol. 93, Iss. 20 — 15 May 2016

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