Carrier density dependence of superconducting transition temperature of electron-doped SrTiO based on the first-principles calculations

Ikaida, Riku*; Sano, Kazuhiro*; Masuda, Yoshimi*; Sekikawa, Takuya; Ono, Yoshiaki*

The superconductivity of SrTiO, which is used in solar cells and as a photocatalyst, is observed in systems doped with electrons such as Nb, but it also exhibits crystal instability due to doping, and the realization of superconductivity is in competition with doping and crystal instability. Since the crystal instability is not well understood, we calculated the electronic structure of SrTiO with electron doping as a parameter using the first-principles calculation software Quantum ESPRESSO. As a result, we succeeded in obtaining a solution for the decrease in frequency of crystal vibration (softening), which is considered to be caused by the ferroelectric transition, by reducing the amount of electron doping, and at the same time, we obtained the result that the superconducting transition temperature increases. This result is consistent with the experimental results of previous studies. This study provides new insight into the mechanism of superconductivity in SrTiO, which has been an unsolved problem for many years.