Orbital-selective metal-insulator transition lifting the t2g band hybridization in the Hund metal Sr3(Ru1-xMnx)2 O7

Abstract

We reveal the orbital-selective metal-insulator transition in a 4d multiorbital system, Sr3(Ru1-xMnx)2O7(x=0-0.2), by means of angle-resolved photoemission spectroscopy. With a small substitution (x=0.05) of Mn with localized 3d orbitals, the spectra for the 4dxy band become incoherent with a large gap, while the 4dxz/yz bands stay metallic with sharp quasiparticle peaks. Intriguingly, this lifts band hybridization among 4d orbitals, and causes a two- to one-dimensional crossover in the remaining Fermi surface. Significant nesting in the remaining Fermi surface is implied to induce the reported magnetic ordering, and yields the insulating bulk state at higher Mn substitution, where all bands are gapped and totally incoherent. The availability of orbital-selective tuning of the pseudogap by a small impurity will prompt further theoretical studies of Hund's metals, which were recognized only recently in condensed matter physics.