2013, Allan, M.P., Tamai, A., Rozbicki, E., Fischer, M.H., Voss, J., King, P.D.C., Meevasana, W., Thirupathaiah, S., Rienks, E., Fink, J., Tennant, D.A ., Perry, R.S., Mercure, J.F., Wang, M.A., Lee, Jinho, Fennie, C.J., Kim, E.A., Lawler, M.J., Shen, K.M., Mackenzie, A.P., Shen, Z.X., Baumberger, F.

The phase diagram of Sr3Ru2O7 shows hallmarks of strong electron correlations despite the modest Coulomb interaction in the Ru 4d shell. We use angle-resolved photoelectron spectroscopy measurements to provide microscopic insight into the formation of the strongly renormalized heavy d-electron liquid that controls the physics of Sr3Ru2O7. Our data reveal itinerant Ru 4d-states confined over large parts of the Brillouin zone to an energy range of <6 meV, nearly three orders of magnitude lower than the bare band width. We show that this energy scale agrees quantitatively with a characteristic thermodynamic energy scale associated with quantum criticality and illustrate how it arises from a combination of back-folding due to a structural distortion and the hybridization of light and strongly renormalized, heavy quasiparticle bands. The resulting heavy Fermi liquid has a marked k-dependence of the renormalization which we relate to orbital mixing along individual Fermi surface sheets.