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

TL;DR

This study investigates charge dynamics in a frustrated fermionic system on a triangular lattice, revealing distinct behaviors in charge-ordered phases and highlighting the effects of frustration on optical spectra.

Contribution

It provides a detailed analysis of charge dynamics in a spinless fermion model on a frustrated lattice, emphasizing the role of frustration in optical and correlation spectra, which is novel.

Findings

Optical spectra in CO_1/3 show multiple components with low-energy weights persisting below T_CO.

Charge correlation changes in CO_1/3 are weakly momentum dependent below T_CO.

Charge frustration effects explain the characteristic dynamics observed, aligning with experimental spectra.

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, in zero and finite temperatures by the exact diagonalization methods. We focus on the two charge ordered (CO) phases, termed CO_1/2 and CO_1/3, which, respectively, are realized by the inter-site Coulomb interaction and the quantum/thermal fluctuations. The optical spectra in CO_1/3 show multiple components and their low-energy weights are survived even below the ordering temperature (T_CO). Changes of the dynamical charge correlation below T_CO in CO_1/3 are weakly momentum dependent, in sharply contrast to CO_1/2. These characteristic dynamics in CO_1/3 are attributable to the charge frustration effects, and reproduce some aspects of the recent experimental optical and x-ray scattering spectra.