Magnetically driven orbital-selective insulator–metal transition in double perovskite oxides

Interaction-driven metal–insulator transitions or Mott transitions are widely observed in condensed matter systems. In multi-orbital systems, many-body physics is richer in which an orbital-selective metal–insulator transition is an intriguing and unique phenomenon. Here we use first-principles calculations to show that a magnetic transition (from paramagnetic to long-range magnetically ordered) can simultaneously induce an orbital-selective insulator–metal transition in rock-salt ordered double perovskite oxides A 2 BB ′O 6 , where B is a non-magnetic ion (Y 3+ and Sc 3+ ) and B ′ a magnetic ion with a d 3 electronic configuration (Ru 5+ and Os 5+ ). The orbital-selectivity originates from geometrical frustration of a face-centered-cubic lattice on which the magnetic ions B ′ reside. Including realistic structural distortions and spin-orbit interaction do not affect the transition. The predicted orbital-selective transition naturally explains the anomaly observed in the electric resistivity of Sr 2 YRuO 6 . Implications of other available experimental data are also discussed. This work shows that by exploiting geometrical frustration on non-bipartite lattices, new electronic/magnetic/orbital-coupled phase transitions can occur in correlated materials that are in the vicinity of metal–insulator phase boundary. Metal–insulator transitions: Magnetically-driven Mott transition in double perovskite oxides First-principle calculations shed new light on orbital-selective Mott transitions in magnetic perovskites, providing new insight and explaining existing data. A Mott transition is a metal–insulator transition whereby electric-field screening causes the potential felt by electrons to become strongly peaked, making the electrons localized. In multi-orbital systems an orbital-selective Mott transition can occur: electrons become localized on some orbitals but remain itinerant on the others. Hanghui Chen from New York University Shanghai in China uses first-principle calculations to show that a magnetic transition can induce an orbital-selective Mott transition in an ordered double perovskite oxide, in which the occurrence of long-range magnetic order makes electrons in one orbital metallic while leaving the others insulating. This is related to geometrical frustration in the magnetic lattice, and structural distortions and spin-orbit interactions do not affect the transition.