Large Kohn anomaly and phonon collapse induced by charge density wave in UPt₂Si₂

2024/12/13 by Jooseop Lee, Greta Chappell, Lee, Jooseop +7
Engineering · Materials Science · Physics and Astronomy · #Semiconductor materials and devices #Electronic and Structural Properties of Oxides #Rare-earth and actinide compounds

paper · pdf · doi:10.48550/arxiv.2412.10346

Abstract

Using high-energy-resolution inelastic x-ray scattering, we observe anomalous softening and damping of the transverse acoustic phonon in UPt₂Si₂ as the system is cooled towards the charge density wave (CDW) transition temperature, T_\rmCDW. The phonon exhibits a marked Kohn-type anomaly around the CDW wave vector, Q_\rmCDW, and becomes overdamped within a finite momentum range already well above T_\rmCDW. The dispersion anomaly is consistent with potential Fermi surface nesting, which together with the extended phonon collapse indicate strong electron-phonon coupling. The transition temperature estimated from the phonon softening is markedly lower than T_\rmCDW, consistent with a primarily electronic instability rather than a phonon-driven transition. Our results establish UPt₂Si₂ as a prime example of a strongly correlated electron CDW system with exceptionally strong electron-phonon coupling driving phonon softening and collapse.

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