Avoidance of magnetic frustration: charge and magnetic ordering in the triangular lattice Hubbard model

Geometrically frustrated magnetic materials and models have attracted significant

attention in the condensed matter community because they are apt to exhibit interesting

collective phases of matter. Geometric frustration arises in magnetic systems when all

nearest neighbor antiferromagnetic interactions cannot be minimized simultaneously.

A similar phenomenon is observed in itinerant systems, metals, because the hopping,

kinetic energy, of electrons between nearest neighbor ions does not promote a minimization

of the repulsive electron-electron interactions. We study the paradigm

extended Hubbard model of interacting electrons on the geometrically frustrated

triangular lattice. We report results from mean field calculations for a model with

an average electron filling of n = 2/3, where electrons could avoid geometric frustration

if they all were to occupy sites that define a honeycomb substructure of the parent

triangular lattice. At T = 0 K, we find that a partially ordered charge and magnetic phase

forms on a honeycomb substructure at a critical on-site interaction U_c/t = 5.00. We report

the effects of finite nearest neighbor Coulomb repulsion, V/t, and finite temperature

on the properties of our model.