  Two-dimensional Na$_3$Bi is a dual topological insulator protected by
time-reversal and mirror symmetry, resulting in a promising platform for
devices design. However, in reality, the design of topological devices is
hindered by a sensitivity against disorder and temperature. We study the
topological properties of Na$_3$Bi in the presence of intrinsic defects,
investigating the robustness of the edge states and the resulting transport
properties. We apply a recursive Green's function technique enabling the study
of disordered systems with lengths comparable to experimentally synthesized
materials, in the order of micrometers. We combine our findings to propose a
topological insulator device, where intrinsic defects are used to filter the
response of trivial bulk states. This results in a stable conductance
throughout a large range of electronic temperatures, and controllable by a
perpendicular electric field. Our proposal is general, enabling the design of
various dual topological insulators devices.

Mesoscale and Nanoscale Physics