Interface-induced topological insulator transition in GaAs/Ge/GaAs quantum wells.

We demonstrate theoretically that interface engineering can drive germanium, one of the most commonly used semiconductors, into a topological insulating phase. Utilizing giant electric fields generated by charge accumulation at GaAs/Ge/GaAs opposite semiconductor interfaces and band folding, the new design can reduce the sizable gap in Ge and induce large spin-orbit interaction, which leads to a topological insulator transition. Our work provides a new method to realize topological insulators in commonly used semiconductors and suggests a promising approach to integrate it in well-developed semiconductor electronic devices.