Contrasted Sn substitution effects on Dirac line node semimetals SrIrO3 and CaIrO3

Perovskite-type iridates SrIrO3 and CaIrO3 are a Dirac line node semimetal protected by crystalline symmetry, providing an interesting playground to investigate electron correlation effects on topological semimetals. The effect of Sn doping was examined by growing SrIr1−xSnxO3 and CaIr1−xSnxO3 thin films epitaxially on the SrTiO3(001) substrate using pulsed laser deposition. Upon Sn doping, the semimetallic ground state switches into an insulator. As temperature is lowered, the resistivity, ρ(T), of SrIr1−xSnxO3 above a critical doping level (xc ∼ 0.1) shows a well-defined transition from the semimetal to a weakly ferromagnetic insulator at T = Tc. In contrast, ρ(T) of CaIr1−xSnxO3 with increasing x shows a rapid increase in magnitude but does not show a clear signature of metal-insulator transition in the temperature dependence. We argue that the contrasted behavior of the two closely related iridates reflects the interplay between the effects of electron correlation and disorder enhanced by Sn doping.