Magnetoelastic hybrid excitations in CeAuAl3
2019
Nearly a century of research has established the
Born–Oppenheimer approximationas a cornerstone of condensed-matter systems, stating that the motion of the atomic nuclei and electrons may be treated separately. Interactions beyond the
Born–Oppenheimer approximationare at the heart of
magneto-elastic functionalities and instabilities. We report comprehensive
neutron spectroscopyand ab initio phonon calculations of the coupling between phonons, CEF-split localized 4f electron states, and conduction electrons in the paramagnetic regime of C e A u A l 3 , an archetypal Kondo lattice compound. We identify two distinct
magneto-elastic hybrid excitations that form even though all coupling constants are small. First, we find a CEF–phonon bound state reminiscent of the vibronic bound state (VBS) observed in other materials. However, in contrast to an abundance of optical phonons, so far believed to be essential for a VBS, the VBS in C e A u A l 3 arises from a comparatively low density of states of acoustic phonons. Second, we find a pronounced anticrossing of the CEF excitations with acoustic phonons at zero magnetic field not observed before. Remarkably, both
magneto-elastic excitations are well developed despite considerable damping of the CEFs that arises dominantly by the conduction electrons. Taking together the weak coupling with the simultaneous existence of a distinct VBS and anticrossing in the same material in the presence of damping suggests strongly that similarly well-developed
magneto-elastic hybrid excitations must be abundant in a wide range of materials. In turn, our study of the excitation spectra of C e A u A l 3 identifies a tractable point of reference in the search for
magneto-elastic functionalities and instabilities.
Keywords:
-
Correction
-
Source
-
Cite
-
Save
-
Machine Reading By IdeaReader
74
References
17
Citations
NaN
KQI