Non-Conventional Critical Behavior and Q-dependent Electron-Phonon Coupling Induced Phonon Softening in the CDW Superconductor LaPt2Si2

Abstract

This paper reports the first experimental observation of phonons and their softening on single crystalline LaPt${}_2$Si${}_2$ via inelastic neutron scattering. From the temperature dependence of the phonon frequency in close proximity to the charge-density wave (CDW) $q$-vector, we obtain a CDW transition temperature of T${}_{CDW}$ = 230 K and a critical exponent $\beta$ = 0.28 $\pm$ 0.03. This value is suggestive of a non-conventional critical behavior for the CDW phase transition in LaPt${}_2$Si${}_2$, compatible with a scenario of CDW discommensuration (DC). The DC would be caused by the existence of two CDWs in this material, propagating separately in the non equivalent (Si1-Pt2-Si1) and (Pt1-Si2-Pt1) layers respectively, with transition temperatures T${}_{CDW-1}$ = 230 K and T${}_{CDW-2}$ = 110 K. A strong $q$-dependence of the electron-phonon coupling has been identified as the driving mechanism for the CDW transition at T${}_{CDW-1}$ = 230 K while a CDW with 3-dimensional character, and Fermi surface quasi-nesting as a driving mechanism, is suggested for the transition at T${}_{CDW-2}$ = 110 K. Our results clarify some aspects of the CDW transition in LaPt${}_2$Si${}_2$, which have been so far misinterpreted by both theoretical predictions and experimental observations, and give direct insight into its actual temperature dependence.

References in corpus (10)

• Ubiquitous Interplay between Charge Ordering and High-Temperature Superconductivity in Cuprates
• Extended Phonon Collapse and the Origin of the Charge-Density-Wave in NbSe${}_2$
• Two energy gaps and Fermi surface 'arcs' in NbSe2
• Tuning the Charge Density Wave and Superconductivity in CuxTaS2
• Electron-Phonon Coupling and the Soft Phonon Mode in TiSe${}_2$
• Phonon anharmonicity: a pertinent review of recent progress and perspective
• A crossover in phase diagram of NaFe${}_{1-x}$Co${}_x$As determined by electronic transport measurements
• Evolution of charge density wave order and superconductivity under pressure in LaPt${}_2$Si${}_2$
• Multigap Superconductivity in a charge density wave superconductor LaPt2Si2
• Nodeless superconductivity in the charge density wave superconductor LaPt${}_2$Si${}_2$

Cited by in corpus (2)

• Emergent properties and the multiscale characterization challenge in condensed matter, from crystals to complex materials: a Review
• Structural Evolution and Onset of the Density Wave Transition in the CDW Superconductor LaPt${}_2$Si${}_2$ Clarified with Synchrotron XRD