Spin-orbital gap of multiorbital antiferromagnet

TL;DR

This paper investigates the spin-gap formation in a multiorbital frustrated system by analyzing an e_g-orbital Hubbard model, revealing a spin-orbital gap influenced by orbital arrangements and spin frustration.

Contribution

It demonstrates how orbital arrangements affect spin gaps in multiorbital systems using advanced numerical methods and effective modeling.

Findings

Finite spin-orbital gap observed in strongly frustrated regions.

Ferro-orbital arrangement simplifies the system to an effective one-orbital model.

Spin frustration degree is controlled by orbital spatial anisotropy.

Abstract

In order to discuss the spin-gap formation in a multiorbital system, we analyze an e_g-orbital Hubbard model on a geometrically frustrated zigzag chain by using a density-matrix renormalization group method. Due to the appearance of a ferro-orbital arrangement, the system is regarded as a one-orbital system, while the degree of spin frustration is controlled by the spatial anisotropy of the orbital. In the region of strong spin frustration, we observe a finite energy gap between ground and first-excited states, which should be called a spin-orbital gap. The physical meaning is clarified by an effective Heisenberg spin model including correctly the effect of the orbital arrangement influenced by the spin excitation.