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Title: Forbidden phonon: Dynamical signature of bond symmetry breaking in the iron chalcogenides

Investigation of the inelastic neutron scattering spectra in Fe1+yTe1₋xSex near a signature wave vector Q=(1,0,0) for the bond-order wave (BOW) formation of parent compound Fe1+yTe reveals an acoustic-phonon-like dispersion present in all structural phases. While a structural Bragg peak accompanies the mode in the low-temperature phase of Fe1+yTe, it is absent in the high-temperature tetragonal phase, where Bragg scattering at this Q is forbidden by symmetry. Notably, this mode is also observed in superconducting FeTe0.55Se0.45, where structural and magnetic transitions are suppressed, and no BOW has been observed. Lastly, the presence of this “forbidden” phonon indicates that the lattice symmetry is dynamically or locally broken by magneto-orbital BOW fluctuations, which are strongly coupled to lattice in these materials.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [3] ;  [3]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
  2. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research; Univ. of Maryland, College Park, MD (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
Publication Date:
OSTI Identifier:
1336201
Report Number(s):
BNL--113204-2016-JA
Journal ID: ISSN 2469-9950; PRBMDO; R&D Project: PO010; KC0201060
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 12; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (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