CONSIDERATION OF EXCITON MODELS TO EXPLAIN SUPERCONDUCTIVITY TRANSITION ABOVE 150-K IN HGBA2CA2CU3O8-HIGH PRESSURE(DELTA AT ULTRA)

It has been recently reported that the shoulder of the superconducting transition in HgBa2Ca2Cu3O8+delta can be elevated from ca. 133 K to c a. 153 K as pressure (P) is raised from 1 atm (ca. 10(5) Pa) to 150 kb ar (1.5 x 10(10) Pa). The data show an approximately linear T(c) again st P up to ca. 17 kbar (1.7 x 10(9) Pa) (hydrostatic), and thereafter (non-hydrostatic) indication of saturation or slope change. It is the purpose of this paper to discuss this pressure enhancement in terms of two general theories of exciton-induced high-T(c) superconductivity, namely the viewpoint of the virtual exciton and that of the condensati on of excitons.