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

David M. Fobes, Igor A. Zaliznyak, John M. Tranquada, Zhijun Xu, Genda Gu, Xu-Gang He, Wei Ku, Yang Zhao, Masaaki Matsuda, V. Ovidiu Garlea, and Barry Winn
Phys. Rev. B 94, 121103(R) – Published 1 September 2016
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Abstract

Investigation of the inelastic neutron scattering spectra in Fe1+yTe1xSex near a signature wave vector Q=(1,0,0) for the bond-order wave (BOW) formation of parent compound Fe1+yTe [D. Fobes et al., Phys. Rev. Lett. 112, 187202 (2014)] 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. 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.

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  • Received 21 September 2015
  • Revised 28 July 2016

DOI:https://doi.org/10.1103/PhysRevB.94.121103

©2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

David M. Fobes1,*, Igor A. Zaliznyak1,†, John M. Tranquada1, Zhijun Xu1, Genda Gu1, Xu-Gang He1, Wei Ku1, Yang Zhao2,3, Masaaki Matsuda4, V. Ovidiu Garlea4, and Barry Winn4

  • 1CMPMSD, Brookhaven National Laboratory, Upton, New York 11973, USA
  • 2NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
  • 3DMSE, University of Maryland, College Park, Maryland 20742, USA
  • 4QCMD, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • *dfobes@bnl.gov
  • zaliznyak@bnl.gov

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Issue

Vol. 94, Iss. 12 — 15 September 2016

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