Large Kohn Anomaly and Phonon Collapse Induced by Charge Density Wave in UPt_{2}Si_{2}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Physics

Background:

• Charge density wave (CDW) transitions are collective electronic phenomena in solids.
• Understanding the interplay between electron correlations, lattice dynamics, and CDW formation is crucial for materials science.

Purpose of the Study:

• To investigate the lattice dynamics and electron-phonon coupling in UPt_{2}Si_{2} near its CDW transition.
• To determine the driving mechanism of the CDW transition in this strongly correlated system.

Main Methods:

• High-energy-resolution inelastic x-ray scattering (IXS) was employed to probe phonon behavior.
• Analysis focused on phonon softening, damping, and Kohn anomalies around the CDW wave vector.

Main Results:

• Anomalous softening and damping of a transverse acoustic phonon were observed as temperature decreased towards T_{CDW}.
• A Kohn-type anomaly was identified at the CDW wave vector, with significant overdamping occurring well above T_{CDW}.
• The observed phonon anomalies suggest strong electron-phonon coupling and potential Fermi surface nesting.

Conclusions:

• The results indicate that UPt_{2}Si_{2} is a prime example of a strongly correlated electron system exhibiting strong electron-phonon coupling.
• The transition is primarily driven by an electronic instability, not a phonon-driven instability, as evidenced by the phonon softening behavior.
• UPt_{2}Si_{2} serves as a model system for studying CDW formation influenced by strong electron-phonon interactions.