Engineering three dimensional topological insulator in layered heterostructures

We show that three dimensional topological insulator can be designed artificially via staking layers of two-dimensional Fermi gases (2DEGs) with finite inter-layer tunneling. The approach is based on stacking bilayers of Rashba-type spin-orbit coupled 2DEG with opposite spin-orbit coupling on opposite planes of bilayers. Spin Orbit interaction locks electronic states with respective spin projections, i.e.$+$/-a(k*s) with `a' is the Rashba-spin-orbit coupling strength, `k' is the momentum, and `s' is Pauli matrices for spin. We find that in the stack of bilayers grown along (001)-direction, a topological phase transition occurs above a critical number of Rashba-bilayers, with formation of a single spin-polarized Dirac cone at the $\backslash $Gamma-momentum . This approach offers a path to design artificial topological insulators in a set up that takes full advantage of atomic layer deposition approach, is free from crystal geometry, and is tunable. Work is supported by US DOE and Nordita.