It is helpful to briefly discuss the Jahn-Teller effect in the pseudo-angular momentum language, as this is not entirely intuitive. Consider the term [(LHx )2 − (LHy )2] = 1 2 [ (LH+)2 + (LH−)2] In terms of the Bloch operators LH+ = 2 (b1†b0 + b0†b−1) ...