Avron J.E., Berger J., Last Y.
Piezoelectricity: Quantized Charge Transport Driven by Adiabatic 
Deformations
(145K, postscript)

ABSTRACT.  We study the (zero temperature) quantum piezoelectric response of
Harper-like models with broken inversion symmetry. The charge transport 
in these models is related to topological invariants (Chern numbers). 
We show that there are arbitrarily small periodic modulations of the
atomic positions that lead to nonzero charge transport for the
electrons.