  Motivated by an experimental report of iridate superlattices, we performed
first-principle electronic structure calculations for SrIrO$_3$/SrTiO$_3$.
Heterostructuring causes SrIrO$_3$ to become Sr$_2$IrO$_4$-like, and the system
has the well-defined $j_{\rm eff}$=1/2 states near the Fermi level as well as
canted antiferromagnetic order within the quasi-two-dimensional IrO$_2$ plane.
In response to a larger tensile strain, the band gap is increased due to the
resulting increase in bond length and the bandwidth reduction. The ground state
magnetic properties are discussed in comparison to the metastable collinear
antiferromagnetic state. Our work sheds new light for understanding the recent
experimental results on the iridate heterostructures.
