Korshunov, A. N.Sukhanov, A. S.Gebel, S.Pavlovskii, M. S.Andriushin, N. D.Gao, Y.Moya, J. M.Morosan, E.Rahn, M. C.2024-08-292024-08-292024Korshunov, A. N., Sukhanov, A. S., Gebel, S., Pavlovskii, M. S., Andriushin, N. D., Gao, Y., Moya, J. M., Morosan, E., & Rahn, M. C. (2024). Phonon softening and atomic modulations in ${\mathrm{EuAl}}_{4}$. Physical Review B, 110(4), 045102. https://doi.org/10.1103/PhysRevB.110.045102https://hdl.handle.net/1911/117722EuAl4 is a rare-earth intermetallic in which competing itinerant and/or indirect exchange mechanisms give rise to a complex magnetic phase diagram, including a centrosymmetric skyrmion lattice. These phenomena arise not in the tetragonal parent structure but in the presence of a charge-density wave (CDW), which lowers the crystal symmetry and renormalizes the electronic structure. Microscopic knowledge of the corresponding atomic modulations and their driving mechanism is a prerequisite for a deeper understanding of the resulting equilibrium of electronic correlations and how it might be manipulated. Here, we use synchrotron single-crystal x-ray diffraction, inelastic x-ray scattering, and lattice-dynamics calculations to clarify the origin of the CDW in EuAl4. We observe a broad softening of a transverse acoustic phonon mode that sets in well above room temperature and, at 𝑇CDW=142 K, freezes out in an atomic displacement mode described by the superspace group 𝐼⁢𝑚⁡𝑚⁡𝑚⁡(00⁢𝛾)⁢𝑠⁢00. In the context of previous work, our observation is a clear confirmation that the CDW in EuAl4 is driven by electron-phonon coupling. This result is relevant for a wider family of BaAl4 and ThCr2⁢Si2-type rare-earth intermetallics known to combine CDW instabilities and complex magnetism.engExcept where otherwise noted, this work is licensed under a Creative Commons Attribution (CC BY) license.  Permission to reuse, publish, or reproduce the work beyond the terms of the license or beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.Journal articlePhysRevB-110-045102https://doi.org/10.1103/PhysRevB.110.045102