Speaker
Joel Moore (Berkeley)
(Berkeley)
Description
The original definition of a topological insulator was as a
time-reversal-symmetric insulator in which spin-orbit
coupling leads to protected metallic edge or surface states.
An alternate definition comes from considering the effect
of a small perturbation that breaks the symmetry and gaps
the surfaces; then the material can be viewed as having a
quantized magnetoelectric effect. We discuss
generalizations of this result to other materials and
symmetry classes. In closing we discuss how a version of BF
theory can capture both definitions of a topological
insulator in either 2D or 3D, just as the Chern-Simons
effective theory captures the universal features of quantum
Hall states. Possible generalizations to "fractional"
topological insulators are discussed.
