Resonant Electron–Phonon Interaction and Its Non-Fano-Type Wavelength and Power-Dependent Raman Manifestation

The presence of Fano resonance in a system often proves to be very useful in understanding various electronic and quantum properties of materials, especially in semiconductors. Although identifiable using Raman spectroscopy through the presence of Fano-type characteristics such as asymmetry and antiresonance in spectral line shape, it is difficult to unambiguously identify its presence and nature due to other factors/processes also affecting them. A wavelength- and power-dependent Raman scattering experiment, along with appropriate theoretical analysis, reveals the resonant nature of electron–phonon interaction in the Ag Raman mode (994 cm–1) in orthorhombic V2O5. The asymmetric Raman line shape with an antiresonance dip and an electronic Raman background support the presence of a Fano interaction. The theoretical fitting of experimental data quantifies the electron–phonon coupling strength by the Fano coupling parameter (q). The excitation wavelength-dependent Raman spectra appear to contradict the Fano-type behavior, which has been used to identify the resonant nature of the Fano interaction. The Fano interaction weakens on increasing the excitation power due to the involvement of anharmonic effects.