Intraband collective excitations in fractional Chern insulators are dark

TL;DR

This paper demonstrates that intra-band collective excitations in fractional Chern insulators are optically dark due to their weak coupling to light, based on quantum geometry and plasma analogy insights.

Contribution

It reveals the dark nature of intra-band excitations in fractional Chern insulators and links this to quantum geometry and classical plasma models.

Findings

Intra-band excitations are weakly coupled to light in fractional Chern insulators.

The relationship between quantum geometry and structure factor explains the dark excitations.

Classical plasma analogy supports the weak optical activity of these excitations.

Abstract

The low-energy collective excitations of semiconductors and insulators often couple strongly to light, allowing them to be probed optically. We argue here that in fractional Chern insulators intra-band collective excitations are dark in the sense that they couple anomalously weakly to light. This conclusion is based on a relationship between ideal quantum geometry and the structure factor of a Chern band, and on a classical plasma analogy motivated by the vortexibility property of ideal Chern bands.