The mean field theory of a T and P symmetric spin liquid state is developed. The quasiparticle excitations in the spin liquid state are shown to be spin 1 2 neutral fermions (the spinons) and charge e spinless bosons (the holons). The spin liquid state is shown to be characterized by a non-trivial topological order. Although our discussions are based on the mean field theory, the concept of the topological order and the associated universal properties (e.g., the quantum number of the quasiparticles) are expected to be valid beyond the mean field theory. We also discuss the dynamical stability of the mean field theory.

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