LOWERING OF BOSON-FERMION SYSTEM ENERGY WITH AGAPPED COOPER RESONANT-PAIR DISPERSION RELATION

摘要

Applying two-time Green-function techniques to the Friedberg-T.D. Lee phenomenolog-ical Hamiltonian of a many-fermion system, it is shown that positive-energy resonantbosonic pairs associated with four-fermion excitations above the Fermi sea are ener-getically lower in a ground-state that is a mixture of two coexisting and dynamicallyinteracting many-particle subsystems: a) unpaired fermions and b) composite bosons. Itis argued that an interaction between free fermions and bosons excited above the Fermisea in the mixture, namely, the continuous processes of pair-formation from, and disinte-gration into, two unpaired electrons, results in a substantially lowering the total systemenergy. The positive-energy composite bosons begin to appear incoherently below a de-pairing temperature T~* astheir coupling- and temperature-dependent number densitygradually increases from zero. This leads quite naturally to the pseudogap phenomenonobserved in high-T_c cuprates