  We examine theoretically a possibility of ferroelectricity caused by
electronic charge order without inversion symmetry, motivated by layered iron
oxides. Quantum electronic models in a paired-triangular lattice are analyzed
by utilizing the variational Monte Carlo simulation. Our calculation
demonstrates that combined effects of electron transfer between the layers,
corresponding to quantum fluctuation between the potential minima, and
geometrical frustration promote appearance of an electric polarization. Present
results are in contrast to the conventional manner of quantum fluctuation in
ferroelectricity.
