Hidden phonon-assisted charge density wave transition in BaFe2Al9 revealed by ultrafast optical spectroscopy
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arXiv
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| Autores principales: | , , , , , , , , , , , , |
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| Formato: | Preprint |
| Publicado: |
2025
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| Materias: | |
| Acceso en línea: | |
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| _version_ | 1866918304396869632 |
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| author | Wang, Lei Ma, Mingwei Li, Jiangxu Chen, Liucheng Lu, Bingru Li, Xiang Jin, Feng Chia, Elbert E. M. Luo, Jianlin Chen, Rongyan Liu, Peitao Hong, Fang Wang, Xinbo |
| author_facet | Wang, Lei Ma, Mingwei Li, Jiangxu Chen, Liucheng Lu, Bingru Li, Xiang Jin, Feng Chia, Elbert E. M. Luo, Jianlin Chen, Rongyan Liu, Peitao Hong, Fang Wang, Xinbo |
| contents | The interplay between electronic and lattice degrees of freedom is fundamental to charge density wave (CDW) formation, yet the microscopic origin often remains elusive. Here, we investigate the transient optical response of the intermetallic compound BaFe2Al9 using polarization-resolved ultrafast optical spectroscopy. We identify a discontinuous sign reversal in the transient reflectivity at Tc ~ 110 K, providing unambiguous evidence for the first-order transition. The anisotropic quasiparticle relaxation establishes the three-dimensional nature of the ordered state. Below Tc, a single coherent 1.6 THz oscillation appears abruptly and remains confined to the CDW phase. This mode exhibits weak temperature dependence with negligible softening and is absent in Raman spectra. First-principles calculations imply that it is a precursor phonon at the CDW wave vector with strong electron-phonon coupling. Our results indicate that the CDW in BaFe2Al9 arises from intertwined electronic and lattice instabilities, assisted by a displacive mechanism mediated by a hidden strongly coupled phonon, distinct from conventional amplitude-mode softening scenarios. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_05908 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Hidden phonon-assisted charge density wave transition in BaFe2Al9 revealed by ultrafast optical spectroscopy Wang, Lei Ma, Mingwei Li, Jiangxu Chen, Liucheng Lu, Bingru Li, Xiang Jin, Feng Chia, Elbert E. M. Luo, Jianlin Chen, Rongyan Liu, Peitao Hong, Fang Wang, Xinbo Strongly Correlated Electrons Materials Science The interplay between electronic and lattice degrees of freedom is fundamental to charge density wave (CDW) formation, yet the microscopic origin often remains elusive. Here, we investigate the transient optical response of the intermetallic compound BaFe2Al9 using polarization-resolved ultrafast optical spectroscopy. We identify a discontinuous sign reversal in the transient reflectivity at Tc ~ 110 K, providing unambiguous evidence for the first-order transition. The anisotropic quasiparticle relaxation establishes the three-dimensional nature of the ordered state. Below Tc, a single coherent 1.6 THz oscillation appears abruptly and remains confined to the CDW phase. This mode exhibits weak temperature dependence with negligible softening and is absent in Raman spectra. First-principles calculations imply that it is a precursor phonon at the CDW wave vector with strong electron-phonon coupling. Our results indicate that the CDW in BaFe2Al9 arises from intertwined electronic and lattice instabilities, assisted by a displacive mechanism mediated by a hidden strongly coupled phonon, distinct from conventional amplitude-mode softening scenarios. |
| title | Hidden phonon-assisted charge density wave transition in BaFe2Al9 revealed by ultrafast optical spectroscopy |
| topic | Strongly Correlated Electrons Materials Science |
| url | https://arxiv.org/abs/2510.05908 |