Magnetoelastic hybrid excitations in CeAuAl₃

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• The Born-Oppenheimer approximation separates nuclear and electron motion in condensed matter.
• Interactions beyond this approximation are crucial for magneto-elastic effects.
• Kondo lattice compounds exhibit complex electron correlations.

Purpose of the Study:

• Investigate magneto-elastic coupling in the Kondo lattice compound [Formula: see text].
• Identify and characterize hybrid excitations beyond the Born-Oppenheimer approximation.
• Explore the role of phonons, localized 4f electron states, and conduction electrons.

Main Methods:

• Neutron spectroscopy to probe magnetic and lattice excitations.
• Ab initio phonon calculations for theoretical analysis.
• Study of [Formula: see text] in the paramagnetic regime.

Main Results:

• Discovery of a CEF-phonon bound state (VBS) involving acoustic phonons.
• Observation of a zero-field anticrossing between CEF excitations and acoustic phonons.
• Both excitations observed despite weak coupling and significant CEF damping by conduction electrons.

Conclusions:

• Magneto-elastic hybrid excitations can form even with weak coupling and damping.
• The findings challenge the necessity of optical phonons for VBS formation.
• This work provides a reference for exploring magneto-elastic functionalities in diverse materials.