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.

One aspect of solid-state physics – the study of solid or crystalline compounds –

is exploring the electrical conduction properties of different materials. Solids are

classified according to their capacity to carry electrical current – that is, to

conduct electrons.