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Title: Pressure dependence of coherence-incoherence crossover behavior in KFe 2 As 2 observed by resistivity and As 75 -NMR/NQR

We present the results of 75As nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), and resistivity measurements in KF e2 As 2 under pressure (p). The temperature dependence of the NMR shift, nuclear spin-lattice relaxation time (T 1), and resistivity show a crossover between a high-temperature incoherent, local-moment behavior and a low-temperature coherent behavior at a crossover temperature (T*). T* is found to increase monotonically with pressure, consistent with increasing hybridization between localized 3d orbital-derived bands with the itinerant electron bands. No anomaly in T* is seen at the critical pressure p c= 1.8 GPa where a change of slope of the superconducting (SC) transition temperature T c( p ) has been observed. In contrast, T c( p ) seems to correlate with antiferromagnetic spin fluctuations in the normal state as measured by the NQR 1/T 1 data, although such a correlation cannot be seen in the replacement effects of A in the AFe 2As 2 (A=K,Rb,Cs) family. In the superconducting state, two T 1 components are observed at low temperatures, suggesting the existence of two distinct local electronic environments. The temperature dependence of the short T 1s indicates a nearly gapless state below T c. On the other hand,more » the temperature dependence of the long component 1/T 1Limplies a large reduction in the density of states at the Fermi level due to the SC gap formation. These results suggest a real-space modulation of the local SC gap structure in KFe 2As 2 under pressure.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [1] ;  [1] ;  [1]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy; Univ. of California, Davis, CA (United States). Dept. of Physics
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
  4. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division; Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry
Publication Date:
Report Number(s):
IS-J 9572
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:
AC02-07CH11358; AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 97; Journal Issue: 6; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Research Areas; Pressure effects; Superconductivity; Physical Systems; Strongly correlated systems; Unconventional superconductors; Techniques; Nuclear magnetic resonance; Condensed Matter and Materials Physics
OSTI Identifier:
1422762
Alternate Identifier(s):
OSTI ID: 1420353