Contrasted Sn Substitution effects on Dirac line node semimetals SrIrO$_{3}$ and CaIrO$_{3}$

TL;DR

This study investigates how Sn doping affects the electronic and magnetic properties of Dirac line node semimetals SrIrO₃ and CaIrO₃, revealing contrasting insulator transition behaviors linked to electron correlation and disorder.

Contribution

It provides the first comparative analysis of Sn doping effects on SrIrO₃ and CaIrO₃ thin films, highlighting their different responses in metal-insulator transition mechanisms.

Findings

SrIr₁₋ₓSnₓO₃ becomes an insulator with weak ferromagnetism above a critical doping.

CaIr₁₋ₓSnₓO₃ shows increased resistivity but no clear metal-insulator transition.

Contrasted behaviors are due to interplay of electron correlation and disorder effects.

Abstract

Perovskite-type iridates SrIrO$_{3}$ and CaIrO$_{3}$ 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 SrIr$_{1-x}$Sn$_{x}$O$_{3}$ and CaIr$_{1-x}$Sn$_{x}$O$_{3}$ thin films epitaxially on SrTiO$_{3}$(001) substrate using pulsed laser deposition. Upon Sn doping, the semimetallic ground state switches into an insulator. As temperature is lowered, the resistivity, $\rho (T)$, of SrIr$_{1-x}$Sn$_{x}$O$_{3}$ above a critical doping level ($x_{\text{c}} \sim 0.1$) shows a well-defined transition from the semimetal to a weakly ferromagnetic insulator at $T = T_{\text{c}}$. In contrast, the $\rho (T)$ of CaIr$_{1-x}$Sn$_{x}$O$_{3}$ with increasing $x$ shows a rapid increase of magnitude but does not show 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.