Low-energy electrodynamics of Dirac semimetal phases in the doped Mott insulator Sr2IrO4

Correlated Dirac semimetal phases emerge in lightly doped (Tb- or La-doped) Mott insulator ${\mathrm{Sr}}_{2}\mathrm{Ir}{\mathrm{O}}_{4}$, where a $d$-wave symmetry-breaking order underlying pseudogap plays crucial role determining the nature of degeneracy, i.e., whether it is line node point node. Here, using realistic five-orbital tight-binding model with Hubbard $U$ and semiclassical Boltzmann transport theory, we systematically study low-energy electrodynamic properties paramagnetic ${\mathrm{Sr}}_{2}\mathrm{Ir}{\mathrm{O}}_{4}$. We investigate effects electronic electron doping concentration on band structures optical various phases. calculate intraband conductivity obtain parameters dc conductivity, scattering rate, Drude weight for three phases: two are point-node states observed 3% Tb-doped 5% La-doped other line-node state. Our results show that temperature dependence strong system while weak systems, which consistent available experimental data. Moreover, effective also compare temperature-dependent screening effect Tb- systems graphene as reference. paper provides valuable insight understanding correlated