Semi-Dirac fermions are known to exist at the critical points of
topological phase transitions requiring fine-tuning of the parameters.
We show that robust semi-Dirac points can appear in a heterostructure
consisting of superconducting Sr2IrO4 and a t2g electron system (t2g-ES)
without fine-tuning. They are topologically stable in the presence of
the symmetries of the model, metallic t2g-ES and a single active band in
Sr2IrO4. If the t2g metal is coupled to two different layers of Sr2IrO4
(effectively a multiband superconductor) in a three-layer-structure the
semi-Dirac points can split into two stable Dirac points with opposite
chiralities. A similar transition can be achieved if the t2g-ES supports
intrinsic triplet superconductivity. By considering Sr2RuO4 as an
example of a t2g-ES we predict a rich topological phase diagram as a
function of various parameters.
Robust semi-Dirac points and unconventional topological phase transitions in doped superconducting Sr2IrO4 tunnel coupled to t2g electron systems