ABSTRACT
This chapter is intended to acquaint the reader with a general
notion of topological insulators. The content of the chapter captures
the basic ideas and concepts of the pioneering studies of the two-
dimensional topological insulators (see Refs. [1-7]) and their three-
dimensional counterparts (see Refs. [8-12]). We shall see that
the emergence of topological insulators is a vivid example of the
importance of fundamental symmetries in physics. In our case, it is
the symmetry with respect to the reversal of the direction of time.
We, therefore, begin with a discussion of general ideas about time-
reversal invariance and its breaking, which will lead us step-by-step
to the notion of topological insulators.
