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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 D. Gu, Xu-Gang He, Wei Ku, Yang Zhao, Masaaki Matsuda, V. Ovidiu Garlea, Barry Winn


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 in 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 have been suppressed, and no BOW has been observed. The presence of this "forbidden" phonon indicates that the lattice symmetry is dynamically or locally broken by magnetic or orbital fluctuations, which are strongly coupled to the lattice degrees of freedom in these materials.
Physical Review B


Fobes, D. , Zaliznyak, I. , Tranquada, J. , Xu, Z. , Gu, G. , He, X. , Ku, W. , Zhao, Y. , Matsuda, M. , Ovidiu Garlea, V. and Winn, B. (2016), Forbidden Phonon: Dynamical Signature of Bond Symmetry Breaking in the Iron Chalcogenides, Physical Review B, [online], (Accessed May 29, 2024)


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Created August 31, 2016, Updated October 12, 2021