Charge dynamics in electronic ferroelectric materials, where electronic charge order is responsible for the electric polarization, is studied. Motivated from the layered iron oxide LuFe2O4 with a frustrated geometrical lattice, we introduce the spin-less fermion V-t model in a paired triangular lattice. This model is analyzed by utilizing the exact diagonalization method with the Lanczos algorithm in finite-size clusters. In particular, we focus on frustration effects on the charge dynamics. In the calculation of the ground state phase diagram, the non-polar two-fold charge order (CO) and the polar three-fold CO appear. In the optical conductivity spectra in the polar three-fold CO phase, multiple-peak structures appear in a wide energy range, in contrast to the spectra in the non-polar two-fold CO phase. This is originated from the non-equivalent two sublattices in the three-fold CO phase. The dynamical charge correlation function in the non-polar two-fold CO phase shows low-energy excitation at the wave vectors which correspond to the three-fold CO. This feature becomes remarkable near the phase boundary between the two-fold and three-fold CO phases. These precursor effects are attributed to the frustrated charge ordered system.
ASJC Scopus subject areas
- Physics and Astronomy(all)