LDA plus slave-boson approach to the correlated electronic structure of the metamagnetic bilayer ruthenate Sr3Ru2O7

The combination of the local-density approximation (LDA) with the rotationally invariant slave-boson theory (RISB) is used to investigate the realistic correlated electronic structure of Sr3Ru2O7. From Wannier-downfolding the low-energy band structure to a three-band model for the Ru(t(2g)) states, the interacting problem is solved including intra-and inter-orbital Hubbard terms as well as spin-flip and pair-hopping interactions. Therewith it is possible to obtain valuable insight into the orbital occupations, relevant local spin multiplets, and the fermiology with increasing correlation strength. Besides generic correlation-induced band-narrowing and -shifting, an intriguing quasiparticle structure close to the Fermi level is found in the neighborhood of the notorious gamma(2) pocket in the Brillouin zone. Along the Gamma-X direction in k-space, that structure appears very sensitive to electronic self-energy effects. The subtle sensitivity, connected also to its manifest multi-orbital character, may put this very low-energy structure in context with the puzzling metamagnetic properties of the compound. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim