Phase transition and in-plane anisotropy of GeAs under high pressure

modes of monoclinic GeAs, pressure will induce a 10°-15° deflection in their polarization direction up to 10 GPa, but has no effect on their anisotropy periods. Tetragonal GeAs also exhibits excellent in-plane optical anisotropy with a period of 180°. But different from monoclinic GeAs, both the polarization direction and periods remain stable in its Raman mode under pressure. The result is conducive to understanding the structural stability and anisotropic properties of GeAs.