AbstractCooper-pair distribution function, $$D_{cp}(\omega ,T_c)$$
D
cp
(
ω
,
T
c
)
, is a recent theoretical proposal that reveals information about the superconductor state through the determination of the spectral regions where Cooper pairs are formed. This is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. From this function is possible to obtain the $$N_{cp}$$
N
cp
parameter, which is proportional to the total number of Cooper pairs formed at a critical temperature $$T_c$$
T
c
. Herein, we reported $$D_{cp}(\omega ,T_c)$$
D
cp
(
ω
,
T
c
)
function of the compressed $$D_3S$$
D
3
S
and $$H_3S$$
H
3
S
high-$$T_c$$
T
c
conventional superconductors, including the effect of stable sulfur isotopes in $$H_3S$$
H
3
S
. $$D_{cp}(\omega ,T_c)$$
D
cp
(
ω
,
T
c
)
suggests that the vibration energy range of 10–70 meV is where the Cooper pairs are possible for these superconductors, pointing out the possible importance of the low-energy region on the electron–phonon superconductivity. This has been confirmed by the fact that a simple variation in the low-frequency region induced for the substitution of S atoms in $$H_3S$$
H
3
S
by its stable isotopes can lead to important changes in $$T_c$$
T
c
. The results also show proportionality between $$N_{cp}$$
N
cp
parameter and experimental or theoretical $$T_c$$
T
c
values.
Pressure-dependent topological superconductivity on the surface of FeTe0.5Se0.5
