QSGW+DMFT+BSE description of superconductivity in Sr₂RuO₄

The nature of pairing in Sr₂RuO₄ continues to be widely debated, in particular, the possibility of a triplet origin of Cooper pairs. Its complexity, with multiple low-energy scales involving subtle interplay among spin, charge and orbital degrees of freedom, calls for advanced theoretical approaches which treat on equal footing all electronic effects. We present a novel approach, a detailed \emph{ab initio} theory, coupling quasiparticle self-consistent GW approximation with dynamical mean field theory (DMFT). We report that the superconducting instability has multiple triplet and singlet components. In the unstrained case the triplet eigenvalues are larger than the singlets. Under uniaxial strain, the triplet eigenvalues drop rapidly and the singlet components increase. This is concomitant with our observation of spin and charge fluctuations shifting closer to wave-vectors favoring singlet pairing in the Brillouin zone. We identify a complex mechanism where charge fluctuations and spin fluctuations co-operate in the even-parity channel under strain leading to increment in T_c, thus proposing a novel mechanism for pushing the frontier of T_c in unconventional "triplet" superconductors.