High-Tc superconductivity in H3S: pressure effects on the superconducting critical temperature and Cooper pair distribution function

We use first-principles calculations to study the effects of pressure on the vibrational and superconducting properties of H3S in the cubic Im 3 ¯ m phase for the pressure range where the superconducting critical temperature (Tc) was measured (155-225 GPa). The pressure effects were incorporated using the functional derivative method (FDM). In this paper we present for the first time the Cooper pair distribution functions Dcp( , Tc) for H3S, which will allow us to identify the spectral regions where Cooper pair formation at temperature Tc is more favorable. We analyze in detail the effects of pressure on the electron-phonon spectral density function 2F( ) and the phonon density of states and their relationship with Tc. The FDM manages to reproduce the trend of the pressure dependence of critical temperature, in good agreement with experimental data in the range of 155 to 190 GPa. Dcp( , Tc) suggests that the low-frequency vibration region is where Cooper pairs are possible, which means that S-vibrations have an important role in the superconductivity properties of H3S.