Electron-phonon coupling and superconducting pairing mechanism in doped SrTiO3

The phase diagram of n-doped SrTiO3 (STO) combines intriguing many-body effects observed in many highly researched quantum materials. The STO ground state is close to a quantum critical point, and the strong quantum fluctuations in the material are connected to structural instabilities. Moreover, its normal-state transport properties are heavily altered by strong electron correlations and polaron formation. Central to the STO phase diagram is the superconducting dome, which is insensitive to magnetic impurities and shares many features with unconventional high-$T_C$ superconductors (e.g. cuprates, iron pnictides and chalcogenides). The nature of the pairing interaction is controversial, even though interactions with various bosons have been studied; they include longitudinal optical and soft transverse phonons, plasmons, and ferroelectric fluctuations.



In this talk we present an investigation of superconductivity in doped STO from first principles using the ab initio Migdal-Eliashberg theory. We analyze the effects of electron-phonon couplings and Coulomb effects, compare our results to available experimental data, and discuss possible pairing scenarios.