Theory of a structural phase transition induced by the jahn-teller effect

We present theory a of structural phase transitions in which the lowering of symmetry originates from a Jahn-Teller effect of the ionic constituents with electronic E-type doublets. We consider a model in which the three lowest vibronic states of the Jahn-Teller complexes are well separated from the higher excitations. The static and dynamic properties are studied in an S=1 pseudospin representation. © 1972 The American Physical Society.