A UNIFIED TOTAL-ENERGY APPROACH TO HIGH-TEMPERATURE SUPERCONDUCTIVITYAND LONG-RANGE ORDERING IN SOLIDS

A novel approach to the long-range ordering in solids is proposed in w hich the total energy is minimized with respect to the long-range orde ring parameter. It is shown that the method, on the one hand, reproduc es the classic BCS results for superconductivity, whilst also agreeing with the well established results for the itinerant antiferromagnetis m. Implications of the method for electronically driven superconductiv ity are discussed. It is found that the electron transfer around the F ermi energy promotes superconductivity. This transfer is easier in the soft multi-orbital systems than in the single-band system.