Narrowing of topological bands due to electronic orbital degrees of freedom

TL;DR

This paper shows that orbital degrees of freedom in frustrated lattice systems cause a robust narrowing of topological bands, which is significant for realizing fractional quantum Hall states without fine-tuning parameters.

Contribution

It reveals that orbital degrees of freedom naturally narrow topological bands, simplifying the realization of lattice FQH states in transition metal compounds.

Findings

Orbital degrees of freedom lead to band narrowing.

The effect is robust and does not require fine-tuning.

Relevant to transition metal compounds.

Abstract

The Fractional Quantum Hall (FQH) effect has been predicted to occur in absence of magnetic fields and at high temperature in lattice systems that have flat bands with non-zero Chern number. We demonstrate that the presence of orbital degrees of freedom in frustrated lattice systems leads to a narrowing of topologically nontrivial bands. This robust effect does not rely on a fine-tuning of long-range hopping parameters as do other recent proposals to realize lattice FQH states and is directly relevant to a wide class of transition metal compounds.