Charge Dynamics in a Correlated Fermion System on a Geometrically Frustrated Lattice

Abstract

Charge dynamics in an interacting fermionic model on a geometrically frustrated lattice are examined. We analyze a spinless fermion model on a paired triangular lattice, an electronic model for layered iron oxides, at zero and finite temperatures by the exact diagonalization methods. We focus on the two charge-ordered (CO) phases, termed CO1/2 and CO1/3, which, respectively, are realized by the intersite Coulomb interaction and quantum/thermal fluctuations. The optical spectra in CO1/3 show multiple components and their low-energy weights survive even below the ordering temperature (TCO). The changes in the dynamical charge correlation below TCO in CO1/3 are weakly momentum-dependent, in sharp contrast to those in CO1/2. These characteristic dynamics in CO1/3 are attributable to charge frustration effects and reproduce some aspects of the recent experimental optical and X-ray scattering spectra.