Abstract
The introduction of the concept of topological insulators (TI) has added anew dimension to our understanding of the nature of the insulating state.These novel insulators differ from the well known ones (sometimes referredto as trivial insulators) such as band insulators, Mott insulators,covalent insulators, Anderson insulators in a fundamental way. All theseinsulators including the TIs have bulk band gaps and surface states whichcan carry current. But in TIs the surface states are topologicallyprotected, gapless and have striking spin texture. The surface stateelectrons possess an intrinsic chirality which enables the propagation ofconduction electrons where spin is locked to momentum and backscatteringevents are suppressed. This remarkable surface electronic structure arisesfrom spin-orbit interaction and time reversal invariance, resulting in theformation of odd number of massless Dirac cones in the single particleenergy dispersion. The charge transport through these topologicallyprotected surface states is dissipationless. After a review of theseexciting features of the TIs I will discuss some recent experimentalobservations (Angle Resolved Photo Emission, Scanning TunnelingMicroscopy, Nuclear Magnetic Resonance etc) and their understanding from atheoretical perspective within single particle electronic structure.
