2008/10/31 by Andrew M. Essin, Joel E. Moore, David Vanderbilt · 4 citations
Physics and Astronomy · #cond-mat.mes-hall #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevlett.102.146805
published as Phys. Rev. Lett. 102, 146805 (2009) · 4 pages; minor changes resulting from a change in one reference
The orbital motion of electrons in a three-dimensional solid can generate a pseudoscalar magnetoelectric coupling θ, a fact we derive for the single-particle case using a recent theory of polarization in weakly inhomogeneous materials. This polarizability θ is the same parameter that appears in the "axion electrodynamics" Lagrangian Δ\cal LEM = (θe2 / 2 πh) \bf E ⋅ \bf B, which is known to describe the unusual magnetoelectric properties of the three-dimensional topological insulator (θ=π). We compute θ 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 wavefunction and defines the 3D topological insulator, like the IQHE, in terms of a topological ground-state response function.