2023/07/21 by Arnab Bera, Bera, Arnab, Partha Sarathi Rana +20
Materials Science · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Organic and Molecular Conductors Research #Phase-change materials and chalcogenides #Solid-state spectroscopy and crystallography #Strongly Correlated Electrons (cond-mat.str-el)
paper · pdf · doi:10.48550/arxiv.2307.11459
openalex publication_date 2023/07/21 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Structural phase transition can occur due to complex mechanisms other than simple dynamical instability, especially when the parent and daughter structure is of low dimension. This article reports such an inversion symmetry-breaking structural phase transition in a quasi-1D compound (TaSe4)3I at TS∼ 141~K studied by Raman spectroscopy. Our investigation of collective lattice dynamics reveals three additional Raman active modes in the low-temperature non-centrosymmetric structure. Two vibrational modes become Raman active due to the absence of an inversion center, while the third mode is a soft phonon mode resulting from the vibration of Ta atoms along the \-Ta-Ta-\ chains. Furthermore, the most intense Raman mode display Fano-shaped asymmetry, inferred as the signature of strong electron-phonon coupling. The group theory and symmetry analysis of Raman spectra confirm the displacive-first-order nature of the structural transition. Therefore, our results establish (TaSe4)3I as a model system with broken inversion symmetry and strong electron-phonon coupling in the quasi-1D regime.