Fig. 1 A cartoon dispersion of a topological insulator, showing Dirac dispersing surface states lying in the bulk band gap.
The discovery of topological insulators as a new state of quantum matter has generated much excitement in the condensed matter community over the past two years. Analogous to the quantum Hall states, which are ballistic 1D edge modes surrounding an insulating 2D bulk, topological insulators have "special" 2D surface states around a 3D bulk. The surface states are chiral, spin polarized, and dissipationless - holding great potential for spintronics applications.
In addition, the surface states have Dirac dispersion, which provides another playground to study exotic high energy phenomena in a condensed matter lab. Axions, dyons, anyons and magnetic monopoles are among the high energy phenomena that are expected to be observed. The interface of a topological insulator with a superconductor is expected to produce Majorana fermions that could be used for topological quantum computing.