Supersymmetric mean-field theory of the t-J model

The supersymmetric formulation of the t-J model is studied in this paper at the mean-field level where the delta-T phase diagram is determined. We fou nd that the slave-fermion-like spiral phase is stable at low doping concent ration, and the slave-boson-like d-wave fermionic spin pairing state become s energetically favourable when delta greater than or equal to 0.23. An imp rovement in free energy using Gutzwiller's method lowers the transition dop ing concentration to delta similar or equal to 0.06. We also point out the existence of new branches of excitations in the supersymmetric theory.