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arXiv · 2303.04499

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

Elisabetta Nocerino·Uwe Stuhr·Irene San Lorenzo·Federico Mazza·Daniel Mazzone·Johan Hellsvik·Shunsuke Hasegawa·Shinichiro Asai·Takatsugu Masuda·Arianna Minelli·Zakir Hossain·Arumugam Thamizhavel·Kim Lefmann·Yasmine Sassa·Martin Månsson
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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.

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Elisabetta Nocerino, Uwe Stuhr, Irene San Lorenzo, Federico Mazza, Daniel Mazzone, Johan Hellsvik, Shunsuke Hasegawa, Shinichiro Asai, Takatsugu Masuda, Arianna Minelli, Zakir Hossain, Arumugam Thamizhavel, Kim Lefmann, Yasmine Sassa, Martin Månsson. 2023-03-08. Non-Conventional Critical Behavior and Q-dependent Electron-Phonon Coupling Induced Phonon Softening in the CDW Superconductor LaPt2Si2. https://doi.org/10.1016/j.jsamd.2023.100621

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