Forbidden Phonon: Dynamical Signature of Bond Symmetry Breaking in the Iron Chalcogenides

Published

September 1, 2016

Author(s)

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

Abstract

Investigation of the inelastic neutron scattering spectra in Fe_1+yTe_1-xSe_x near a signature wave vector Q = (1,0,0) for the bond-order wave (BOW) formation in parent compound Fe_1+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 Fe_1+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 FeTe_0:55Se_0:45, 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.

Citation

Physical Review B

Volume

94

Issue

12

Pub Type

Journals

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Citation

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], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=919499 (Accessed December 6, 2024)