title: Magnetoelectric polarizability and axion electrodynamics in crystalline insulators.
abstract: The orbital motion of electrons in a three-dimensional solid can generate a pseudoscalar magnetoelectric coupling theta, a fact we derive for the single-particle case using a recent theory of polarization in weakly inhomogeneous materials. This polarizability theta is the same parameter that appears in the "axion electrodynamics" Lagrangian DeltaL_{EM}=(thetae;{2}/2pih)E.B, which is known to describe the unusual magnetoelectric properties of the three-dimensional topological insulator (theta=pi). We compute theta for a simple model that accesses the topological insulator and discuss its connection to the surface Hall conductivity. The orbital magnetoelectric polarizability can be generalized to the many-particle wave function and defines the 3D topological insulator, like the integer quantum Hall effect, in terms of a topological ground-state response function.
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Essin
authors.forename: Joel E
authors.initials: JE
authors.lastname: Moore
authors.forename: David
authors.initials: D
authors.lastname: Vanderbilt