Phonon anharmonicity and electron-phonon coupling in exfoliated semimetallic 1 <i>T</i> -TiTe ₂ nanoflakes

Abstract Semi-metallic 1 T -TiTe 2 drew considerable interest owing to its intriguing structural properties. The emergence of charge density wave (CDW) in the single-layer 1 T -TiTe 2 rather than bulk suggests that electron-phonon ( e-ph) coupling may play an important role in inducing CDW or superconductivity. The investigation into lattice anharmonicity, which is strongly linked to e-ph coupling, is still lacking. Here, we employed temperature-dependent Raman spectroscopy to investigate the e-ph coupling and anharmonic phonon–phonon ( ph-ph) interactions for the phonon modes in exfoliated 1 T -TiTe 2 thin flakes (∼12 nm). The E g mode exhibits a Breit–Wigner–Fano lineshape with linear frequency redshift, while both the M and A 1g modes show Gaussian/Lorentzian lineshapes with nonlinear softening frequency redshifts. Both E g and A 1g linewidths show anomalous broadening with increasing temperature due to the interplay between the e-ph coupling and anharmonic ph-ph interactions. In contrast, the M mode exhibits monotonic linewidth broadening with temperature due to anharmonic ph-ph interactions. The e-ph coupling constants were extracted to be λ e − ph E g = 0.95 ± 0.09 , λ e − ph M = 0.05 ± 0.006 , and λ e − ph A 1 g = 0.19 ± 0.0 2 . These findings provide a profound understanding of anharmonic ph-ph interactions, e-ph coupling, and their thermodynamic properties in 1 T -TiTe 2 , which can enhance the comprehension of phonon dynamics in various quantum materials.