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Title: Experimental elucidation of the origin of the ‘double spin resonances’ in Ba(Fe1-xCox)2As2

We report a combined study of the spin resonances and superconducting gaps for underdoped ( T c = 19 K), optimally doped ( T c = 25 K), and overdoped ( T c = 19 K) Ba ( Fe 1 - x Co x ) 2 As 2 single crystals with inelastic neutron scattering and angle resolved photoemission spectroscopy. We also 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. But, 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. Thus 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.
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [1] ;  [4] ;  [5] ;  [5] ;  [6] ;  [6] ;  [2] ;  [3] ;  [7] ;  [8] ;  [4] ;  [9]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Physics
  2. Chinese Academy of Sciences (CAS), Beijing (China). Inst. of High Energy Physics
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences and Computer Science and Mathematics Division
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
  6. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource
  7. Rice Univ., Houston, TX (United States). Dept. of Physics and Astronomy
  8. Univ. of California, Berkeley, CA (United States). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division
  9. Univ. of California, Berkeley, CA (United States). Dept. of Physics, Dept. of Materials Science and Engineering; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division
Publication Date:
Grant/Contract Number:
AC05-00OR22725; AC02-05-CH11231; AC03-76SF008; DMR-1308603; 1362219
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 93; Journal Issue: 20; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1393899
Alternate Identifier(s):
OSTI ID: 1254543