Key Role of Orbital Anisotropy in Geometrically Frustrated Electron System

TL;DR

This study uses the density matrix renormalization group method to explore how orbital anisotropy influences the magnetic properties of a geometrically frustrated electron system on different lattice structures.

Contribution

It reveals the contrasting effects of orbital anisotropy on spin gaps and correlations in zigzag chain and ladder lattice geometries.

Findings

Zigzag chain behaves like decoupled Heisenberg chains with near-zero spin gap.

Ladder exhibits robust rung correlations and a finite spin gap.

Abstract

By using the density matrix renormalization group method, we investigate ground- and excited-state properties of the e_g-orbital degenerate Hubbard model at quarter filling for two kinds of lattices, zigzag chain and ladder. In the zigzag chain, the system is effectively regarded as a decoupled double chain of the S=1/2 antiferromagnetic Heisenberg model, and the spin gap is approximately zero, similar to the case of weakly coupled Heisenberg chains. On the other hand, in the ladder, the spin correlation on the rung remains robust and the spin gap exists.