Giant Anomalous Hall Effect due to Double-Degenerate Quasiflat Bands

We propose a novel approach to achieve a giant anomalous Hall effect (AHE) in materials with flat bands (FBs). FBs are accompanied by small electronic bandwidths, which consequently increases the momentum separation (K) within pair of Weyl points and, thus, the integrated Berry curvature. Starting from a simple model with a single pair of Weyl nodes, we demonstrated the increase of K and the AHE by decreasing the bandwidth. It is further expanded to a realistic pyrochlore lattice model with characteristic double-degenerated FBs, where we discovered a giant AHE while maximizing the K with nearly vanishing band dispersion of FBs. We identify that such a model system can be realized and modulated through strain engineering in both pyrochlore and spinel compounds based on first-principles calculations, validating our theoretical model and providing a feasible platform for experimental exploration.

Automated summary

A novel approach to achieve a giant anomalous Hall effect in materials with flat bands by decreasing electronic bandwidth to increase momentum separation is proposed. This approach can be realized experimentally through strain engineering in pyrochlore and spinel compounds.