Abstract
Investigation of the inelastic neutron scattering spectra in near a signature wave vector for the bond-order wave (BOW) formation of parent compound [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 , it is absent in the high-temperature tetragonal phase, where Bragg scattering at this is forbidden by symmetry. Notably, this mode is also observed in superconducting , 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.
- Received 21 September 2015
- Revised 28 July 2016
DOI:https://doi.org/10.1103/PhysRevB.94.121103
©2016 American Physical Society