  What factors fundamentally determine the value of superconducting transition
temperature (Tc) in high temperature superconductors has been the subject of
intense debate. Following the establishment of an empirical law known as
Homes'law, there is a growing consensus in the community that the Tc value of
the cuprate superconductors is closely linked to its superfluid density and
conductivity. However, all the data supporting this empirical law have been
obtained from the ambient-pressure superconductors. In this study, we present
the first high-pressure results about the connection of these two quantities
with Tc, through the studies on the Bi1.74Pb0.38Sr1.88CuO6+delta and
Bi2Sr2CaCu2O8+delta, in which the value of their high-pressure resistivity (the
reciprocal of conductivity) is achieved by adopting our newly established
method, while the value of superfluid density is extracted using the Homes'law.
We highlight that the Tc values are strongly linked the two joint response
factors of magnetic field and electric field, i.e. superfluid density and
conductivity, respectively, implying that the physics governing the
determination of Tc is influenced by the intrinsic electromagnetic fields of
the system.
