2025/12/16 by Matsumura, Takeshi, Hasegawa, Takumi, Nakajima, Ryuma +5
Physics and Astronomy · Materials Science · #Rare-earth and actinide compounds #Physics of Superconductivity and Magnetism #Magnetic and transport properties of perovskites and related materials
paper · doi:10.48550/arxiv.2512.14216
Soft phonon modes in tetragonal CeCoSi, which undergoes a structural transition at T0=12 K followed by antiferromagnetic order at TN=9.5 K, have been investigated using high-resolution inelastic x-ray scattering. Pronounced softening was detected in the transverse acoustic modes corresponding to the (yz+zx)-type monoclinic distortion, consistent with the experimentally determined triclinic structure. Remarkably, the softening persists up to the zone boundary along (0, 0, q), indicating a short correlation length of the lattice instability. This instability, characterized by a Curie-type strain susceptibility, is interpreted as a consequence of the on-site 4f-5d hybridization, which is intrinsic to this crystal structure due to the lack of inversion symmetry at the two Ce sites.