Terahertz induced phase transformation remains largely investigation, in both theoretical and experimental schemes for various material platforms. In this work, we provide a first thorough estimate on Gibbs free energy variation mechanism, and apply such a theory in a Ruddlesden-Popper perovskite material. Both real and imaginary parts of electric susceptibility components have been explored, and it is revealed that collective rotation of Fe-O octahedron could occur in an ultrafast kinetics. See our prediction in recent Applied Physics Letters, at DOI: 10.1063/5.0174032.