BEREZINSKII-KOSTERLITZ-THOULESS TRANSITION IN A SPIN-CHARGE-SEPARATEDSUPERCONDUCTOR

A model for spin-charge-separated superconductivity in two dimensions is introduced where the phases of the spinon and holon order parameter s couple guage invariantly to a statistical gauge field representing c hiral spin fluctuations. The model is analyzed in the continuum limit and in the low-temperature limit. In both cases we find that physical electronic phase correlations show a superconducting-normal phase tran sition of the Berezinskii-Kosterlitz-Thouless type, while statistical gauge-field excitations are found to be strictly gapless. It is argued that the former transition is in the same universality class as that of the XY model. We thus predict a universal jump in the superfluid de nsity at this transition. The normal-to-superconductor phase boundary for this model is also obtained as a function of carrier density, wher e we find that its shape compares favorably with that of the experimen tally observed phase diagram for the oxide superconductors.