The quest for new materials: Can any insulator become topological?

Researchers at the Joint Quantum Institute (JQI) and the California Institute of Technology have shown that it may be possible to take a conventional semiconductor and endow it with topological properties without subjecting the material to extreme environmental conditions or fundamentally changing its solid state structure. In their Nature Physics (appeared online March 13, 2011) article titled "Floquet topological insulator in semiconductor quantum wells", JQI fellow Victor Galitski with colleagues Netanel Lindner and Gil Refael from Caltech provide theoretical verification that such a transition exists.

The key to this prediction, which can be experimentally tested, is the application of microwaves to an otherwise non-topological insulating system. According to the authors, the material can be transformed into what they call a "Floquet topological insulator". As described below, topological states have applications in quantum information science and the new field of spintronics.