Dynamic Jahn-Teller effect for a double acceptor or acceptor-bound exciton in semiconductors: Mechanism for an inverted level ordering

The dynamic Jahn-Teller effect provides a simple mechanism for inverting the ordering of the J=0,2 levels of the two equivalent holes in a neutral double acceptor or an exciton bound at a neutral acceptor. Whereas Hund's rule places the J=2 level below J=0, Jahn-Teller coupling to E and/or T₂ vibrational modes tends to shift J=0 below J=2, while splitting J=2 into its Γ₃ and Γ₅ components. Alternative proposed explanations involving central-cell, Stark, and strain effects fail to introduce the attractive interaction needed to offset the holes's Coulomb repulsion.