Detection of the prototype symmetry of ferroelastic WO₃ domain walls by angle-resolved polarized Raman spectroscopy

The symmetry of a domain wall in ferroelastic WO₃ is analyzed by angle-resolved polarized Raman spectroscopy. We find that a low-energy Raman mode at 46 cm⁻¹ is largely enhanced within the confined region of the domain wall, whose width is presumed to be ∼25 nm from diffusive x-ray scattering. The wall effect on the enhancement of the Raman signal per unit area is estimated to be three times larger than the contribution of the domains. The light-polarization-dependent Raman intensity at the wall is characterized by the symmetric A_1g Raman tensor that is attributed to the prototypic quasitetragonal phase imposed by the ferroelastic compatibility relationship.