PHASE-DIAGRAM OF A 2D METAL SYSTEM WITH A VARIABLE NUMBER OF CARRIERS

It is shown that the phase diagram of a 2D metal undergoing a supercon ducting transition consists of regions of a normal phase where the mod ulus of the order parameter is absent, an ''anomalous normal'' phase w here the modulus of the order parameter is different from zero but the phase of the order parameter is a random quantity, and a Berezinskii- Kosterlitz-Thouless phase. The characteristic temperatures of transiti ons between the phases and the behavior of the chemical potential as a function of the fermion density and temperature are found. (C) 1997 A merican Institute of Physics.