  We show that the superconducting transition temperature Tc of FeSe1-xTex can
be computed to reasonable values in a modified McMillan approach in which the
electron-phonon coupling is amplified by the antiferromagnetism and the
out-of-plane phonons triggered by the tetrahedral lattice sites. This interplay
is not only effective at ambient pressure, but also under hydrostatic
compression. According to our model, the theoretical Tc of the compressed
FeSe0.5Te0.5 agrees with experiment results. More importantly, by taking into
account the interfacial effect between an FeSe monolayer and its SrTiO3
substrate as an additional gain factor, our calculated Tc value is up to 91 K
high, and provides evidence that the strong Tc enhancement recently observed in
such monolayers with Tc reaching 100 K may be due to an enhanced-electron
phonon coupling.
