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Title: Distinguishing S-plus-minus and S-plus-plus electron pairing symmetries by neutron spin resonances in superconducting Sodium-Iron-Cobalt-Arsenic (transitional temperature = 18 Kelvin)

A determination of the superconducting (SC) electron pairing symmetry forms the basis for establishing a microscopic mechansim for superconductivity. For iron pnictide superconductors, the s{sup {+-}}-pairing symmetry theory predicts the presence of a sharp neutron spin resonance at an energy below the sum of hole and electron SC gap energies (E {le} 2{Delta}). Although the resonances have been observed for various iron pnictide superconductors, they are broad in energy and can also be interpreted as arising from the s{sup ++}-pairing symmetry with E {ge} 2{Delta}. Here we use inelastic neutron scattering to reveal a sharp resonance at E = 7 meV in the SC NaFe{sub 0.935}Co{sub 0.045}As (T{sub c} = 18 K). By comparing our experiments with calculated spin-excitations spectra within the s{sup {+-}} and s{sup ++}-pairing symmetries, we conclude that the resonance in NaFe{sub 0.935}Co{sub 0.045}As is consistent with the s{sup {+-}}-pairing symmetry, thus eliminating s{sup ++}-pairing symmetry as a candidate for superconductivity.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [4] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [3] ;  [7] ;  [5]
  1. Los Alamos National Laboratory
  2. University of Tennessee, Knoxville, Tennessee
  3. Institut fur Festkorperforschung, Julich, Germany
  4. The University of Tennessee, Knoxville, Tennessee
  5. Forschungsneutronenquelle Heinz, Garching, Germany
  6. Gemeinsame Forschergruppe HZB, Berlin, Germany
  7. Institute of Physics, Chinese Academy of Sciences, Beijing, China
  8. Sun Yat-Sen University, Guangzhou, China
Publication Date:
OSTI Identifier:
1043014
Report Number(s):
LA-UR-12-21918
TRN: US1203076
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
DOE/LANL
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ELECTRONS; IRON; NEUTRONS; PNICTIDES; RESONANCE; SCATTERING; SPECTRA; SPIN; SUPERCONDUCTIVITY; SUPERCONDUCTORS; SYMMETRY