Abstract
It has been recently reported that the shoulder of the superconducting transition in HgBa
2
Ca
2
Cu
3
O
8+
δ
can be elevated from
ca
. 133K to
ca
. 153 K as pressure (
P
) is raised from 1 atm (
ca
. 10
5
Pa) to 150 kbar (1.5 x 10
10
Pa). The data show an approximately linear
T
c
against
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 condensation of excitons.