A FIELD-THEORY APPROACH TO THE T-J MODEL AND THE SPIN-CHARGE SEPARATION

We analyze the t-J model using the CP1 representation for the slave operators (holons and spinons) which is particularly suited to study the phenomenon of the spin-charge separation in strongly correlated electron systems. In particular, we show that for the one-dimensional t-J model below half-filling the low-energy effective dynamics of the spin and charge degrees of freedom is represented in the continuum limit by a CP1 model with a topological term, minimally coupled to a massless Dirac field with a four-fermion interaction. The bosonic term of this action describes the spin waves produced by the spinons, while the fermionic term represents the low-energy charge excitations. This theory exhibits explicitly a local abelian gauge invariance.