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In this work we study phonon-phonon coupling in bismuth vanadate (BiVO4),known for its second-order transition involving a variety of couplingmechanisms. Using Raman spectroscopy as a probe, we identify two opticalcoupled phonon modes of the VO4 tetrahedron and study them by varying lightpolarization and temperature. The coupling manifests in non-Lorentzianline-shapes of Raman peaks and frequency shifts. We use theoretical frameworkof coupled damped harmonic oscillators to model the coupling and capture thephenomena in the temperature evolution of the coupling parameters. The couplingis negligible at temperatures below 100 K and later increases in magnitude withtemperature until 400 K. The sign of the coupling parameter depends on thelight polarization direction, causing either phonon attraction or repulsion.After 400 K the phonon-phonon coupling diminishes when approaching phasetransition at which the phonon modes change their symmetry and the coupling isno longer allowed.

Phonon-phonon coupling in bismuth vanadate over a large temperature range across the monoclinic phase