Prediction of robust two-dimensional topological insulators based on Ge/Si nanotechnology

Atomistic tight-binding calculations show that two-dimensional topological insulators can be obtained using Ge or Ge/Si nanotechnologies. The strong quantum confinement is used to open energy gaps in the valence band of artificial graphene made of Ge. These gaps are topologically nontrivial due to the combination of the honeycomb nanogeometry and the spin-orbit coupling. Gap widths above 10 meV can be obtained using realistic structures. With light effective masses, a strong spin-orbit coupling, and a high compatibility with microelectronic processes, Ge is an excellent substrate for the fabrication of spintronic devices based on topological insulator states