Wick's Theorem for Spin Operators and Its Relation to the Coupled-Fermion Representation
Yung‐Li Wang, S. Shtrikman, Herbert B. Callen
It is shown that Wick's theorem and the linked diagram expansion theorem for S = ½ operators (applied elsewhere by the authors to discuss antiferromagnetic spin waves) can be derived by a direct application of conventional theorems to the coupled-fermion representation of spin operators.
Journal of Applied Physics•Mar 1, 1966•7 citations