title: Topological nature of polarization and charge pumping in ferroelectrics.
abstract: Electric polarization in insulators is represented by the transferred charge through a shift of the Bloch wave functions induced by an adiabatic change of external parameters Q-->. It is found that this covalent/quantum contribution is determined nonlocally by the topological structure in the Q--> space. The condition for the charge pumping for a cyclic change of Q--> is also obtained. Applications of this picture to various organic ferroelectrics and BaTiO3 are discussed.
authors.affiliation: Spin Superstructure Project, ERATO, Japan Science and Technology Agency, c/o Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Onoda
authors.forename: Shuichi
authors.initials: S
authors.lastname: Murakami
authors.forename: Naoto
authors.initials: N
authors.lastname: Nagaosa