  Topological insulators are characterized by a nontrivial band topology driven
by the spin-orbit coupling. To fully explore the fundamental science and
application of topological insulators, material realization is indispensable.
Here we predict, based on tight-binding modeling and first-principles
calculations, that bilayers of perovskite-type transition-metal oxides grown
along the [111] crystallographic axis are potential candidates for
two-dimensional topological insulators. The topological band structure of these
materials can be fine-tuned by changing dopant ions, substrates, and external
gate voltages. We predict that LaAuO$_3$ bilayers have a
topologically-nontrivial energy gap of about 0.15 eV, which is sufficiently
large to realize the quantum spin-Hall effect at room temperature. Intriguing
phenomena, such as fractional quantum Hall effect, associated with the
nearly-flat topologically-nontrivial bands found in $e_g$ systems are also
discussed.
