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Title: Surprising loss of three-dimensionality in low-energy spin correlations on approaching superconductivity in Fe 1 + y Te 1 - x Se x

We report inelastic neutron scattering measurements of low-energy ( ℏ ω ≲ 10 meV) magnetic excitations in the “11” system Fe 1+y Te 1-x Se x. The spin correlations are two-dimensional (2D) in the superconducting samples at low temperature, but appear much more three-dimensional (3D) when the temperature rises well above T c ~ 15 K, with a clear increase of the (dynamic) spin correlation length perpendicular to the Fe planes. This behavior is extremely unusual; typically, the suppression of thermal fluctuations at low temperature would favor the enhancement of 3D correlations, or even ordering, and the reversion to 2D cannot be naturally explained when only the spin degree of freedom is considered. Our results suggest that the low temperature physics in the 11 system, in particular the evolution of low-energy spin excitations towards superconducting pairing, intrinsically involves changes in orbital correlations.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [7] ;  [7] ;  [8] ;  [9]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.; National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research; Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering; Univ. of California, Berkeley, CA (United States). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.; Stony Brook Univ., NY (United States). Dept. of Physics
  3. Nanjing Univ. (China). National Lab. of Solid State Microstructures and Dept. of Physics; Univ. of California, Berkeley, CA (United States). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Neutron Data Analysis and Visualization Division
  6. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research; Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering
  7. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
  8. Univ. of California, Berkeley, CA (United States). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division
  9. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.; National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research
Publication Date:
Report Number(s):
BNL-114425-2017-JA
Journal ID: ISSN 2469-9950; PRBMDO; R&D Project: PO010; KC0201060; TRN: US1800322
Grant/Contract Number:
SC0012704; AC02-05CH11231; AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 96; Journal Issue: 13; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Natural Science Foundation of China (NNSFC)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1412663
Alternate Identifier(s):
OSTI ID: 1398296; OSTI ID: 1426556