Neutron Scattering Uncovers Hybrid Excitations from Magnetoelastic Coupling

Great efforts have been devoted to the study of novel ground state behaviors in strongly correlated electron systems in condensed matter physics, often involving intricate lattice and spin dynamics. Inelastic neutron scattering spectroscopy is an indispensable tool for probing these dynamics, offering unique insights into the fundamental interactions governing these systems.

A critical aspect emphasized in these systems is magnetoelastic coupling, which arises from the coupling of spins to the strains. This effect profoundly impacts how these systems behave; as lead author Ma notes in the paper, "With such effect, the magnetic excitations and the lattice vibrations could no longer be studied independently." Instead, the low-lying elementary excitation spectra are modified, leading to the formation of distinct hybrid excitations. These can manifest as crystal electric field (CEF)-phonon vibrons, CEF-phonon anticrossing, and magnon-phonon anticrossing, which occur at specific positions in the reciprocal space.

The emergence of these hybrid excitations highlights that traditional methods separating magnetic and lattice contributions are insufficient to capture the true nature of their low-lying elementary excitation spectra. In this review, recent progress in experimental studies with the generalization of the original phenomenological model, and possible challenges in the study of magnetoelastic coupling in f-electron compounds are surveyed.