Structure and Raman scattering of Cs₃C₆₀ under high pressure

Raman scattering is studied for a pressure-induced superconductor Cs₃C₆₀ in a pressure region from 1 bar to 62 kbar. The center frequency ω₀ for H_g(1) and H_g(2) Raman peaks increase by applying pressure, but the increase shows a saturation in the high-pressure region. On the other hand, the ω₀ for A_g(1) and A_g(2) modes increase monotonically in all pressure regions. The electron-phonon coupling constant for Cs₃C₆₀ shows a rapid decrease up to 30 kbar and an increase above 30 kbar. This result may be associated with a transformation from a multiphase (body-centered orthorhombic and A 15 phases) to a single phase around 20 kbar. X-ray powder diffraction pattern at 11 K under a pressure of 40 kbar shows that a superconducting phase for Cs₃C₆₀ is body-centered orthorhombic.