Nature of spin-charge separation in the t-J model

Quasiparticle properties are explored in an effective theory of the t-J mod el which includes two important components: spin-charge separation and unre normalizable phase shift. We show that the phase shift effect indeed causes the system to be a non-Fermi liquid as conjectured by Anderson on general grounds. But this phase shift also drastically changes a conventional perce ption of quasiparticles in a spin-charge separation state: an injected hole will remain stable due to the confinement of spinon and holon by the phase shift field despite the background is a spinon-holon sea. True deconfineme nt only happens in the zero-doping limit where a bare hole will lose its in tegrity and decay into holon and spinon elementary excitations. The Fermi-s urface structure is completely different in these two cases, from a large b and-structure-like one to four Fermi points in one-hole case, and we argue that the so-called underdoped regime actually corresponds to a situation in between, where the ''gaplike'' effect is amplified further by a microscopi c phase separation at low temperature. Unique properties of the single-elec tron propagator in both normal and superconducting states are studied by us ing the equation of motion method. We also comment on some influential idea s proposed in the literature related to the Mott-Hubbard insulator and offe r a unified view based on the present consistent theory.