Schwinger-boson studies of thet-Jmodel: A self-consistent systematic expansion

A self-consistent systematic expansion is developed for the t-J model in the Schwinger-boson\udapproach. We treat the fermion part with use of a systematic loop expansion technique and study\udthe effects of magnetic fluctuations on the normal-state properties. It is found that the hole motion is\udstrongly renormalized and incoherent bands are produced by magnetic fluctuations. The conductivity\udand the electron density of states are calculated and shown to be anomalous. The antiferromagnetic\udnature of fluctuations is found to be essential for these unusual properties. The relevance of the\udobtained results to oxide superconductors is also discussed