A Theory of Cooperative Jahn-Teller Effect: Structural Phase Transition in CsCuCl_3

Abstract

A theory of the cooperative Jahn-Teller effect is developed toelucidate a structural phase transition observed in the CsCuCl₃crystal. This theory establishes the relationship between the localand the cooperative Jahn-Teller effect. We find that the helicalalignment of Cl^- ions along the c-axis agrees with experimentaldata when the two Δ₆ modes of the phonons executed bythe Cl^- ions contribute to the structutal phase transition.