Investigating Effect of Decoherence on Fano Interference through Raman Spectroscopy

In this paper, we report on the influence of structural and thermal decoherence on the Raman line shape undergoing Fano interference. Using BaTiO₃ as a model sample, we examine its well-known ∼180 cm⁻¹ Raman mode that originates due to the Fano interference between a discrete phonon (A₁(TO₁)) at 172 cm⁻¹, and the continuum formed by the 250 cm⁻¹ (A₁(TO₂)) phonons. Additionally, the asymmetric ∼521 cm⁻¹ mode in p-type doped silicon is examined. The decoherence is demonstrated by introducing random phase fluctuation to the energy-dependent scattering phase Δ(ε) appearing in the typical Fano treatment with the help of a stochastic Monte Carlo approach, and a complete methodology is presented to explain the changes in the Raman line shape. Our approach successfully explains observed changes in the intensity and line shape of mode, suggesting that decoherence is a crucial factor controlling the Raman profiles.