Properties and application of the SO(3) Majorana representation of spin: equivalence with the Jordan-Wigner transformation and exact Z₂ gauge theories for spin models

We explore the properties of the SO(3) Majorana representation of spin. Based on its non-local nature, it is shown that there is an equivalence between the SO(3) Majorana representation and the Jordan-Wigner transformation in one and two dimensions. From the relation between the SO(3) Majorana representation and one-dimensional Jordan-Wigner transformation, we show that application of the SO(3) Majorana representation usually results in $Z_{2}$ gauge structure. Based on lattice Chern-Simons gauge theory, it is shown that the anti-commuting link variables in the SO(3) Majorana representation make it equivalent to an operator form of compact $\text{U(1)}_{1}$ Chern-Simons Jordan-Wigner transformation in 2d. As examples of its application, we discuss two spin models, namely the quantum XY model on honeycomb lattice and the $90^{\circ}$ compass model on square lattice. It is shown that under the SO(3) Majorana representation both spin models can be exactly mapped into $Z_{2}$ gauge theory of spinons, with the standard form of $Z_{2}$ Gauss law constraint.