  Topological insulator (TI) states have been demonstrated in materials with
narrow gap and large spin-orbit interactions (SOI). Here we demonstrate that
nanoscale engineering can also give rise to a TI state, even in conventional
semiconductors with sizable gap and small SOI. Based on advanced
first-principles calculations combined with an effective low-energy k*p
Hamiltonian, we show that the intrinsic polarization of materials can be
utilized to simultaneously reduce the energy gap and enhance the SOI, driving
the system to a TI state. The proposed system consists of ultrathin InN layers
embedded into GaN, a layer structure that is experimentally achievable.
