Approaching quantum anomalous Hall effect in proximity-coupled YIG/graphene/h-BN sandwich structure

TL;DR

This paper demonstrates enhanced magnetic proximity effects in a YIG/graphene/h-BN heterostructure, showing potential for realizing the quantum anomalous Hall effect through gate-tunable anomalous Hall conductance.

Contribution

It introduces a novel YIG/graphene/h-BN sandwich structure that significantly enhances magnetic proximity coupling and exhibits gate-dependent anomalous Hall effects.

Findings

Anomalous Hall conductance reaches 1/4 of the quantum value near the Dirac point.

Exchange coupling strength is as high as 27 meV.

Fermi level tuning controls the anomalous Hall conductance.

Abstract

Quantum anomalous Hall state is expected to emerge in Dirac electron systems such as graphene under both sufficiently strong exchange and spin-orbit interactions. In pristine graphene, neither interaction exists; however, both interactions can be acquired by coupling graphene to a magnetic insulator (MI) as revealed by the anomalous Hall effect. Here, we show enhanced magnetic proximity coupling by sandwiching graphene between a ferrimagnetic insulator yttrium iron garnet (YIG) and hexagonal-boron nitride (h-BN) which also serves as a top gate dielectric. By sweeping the top-gate voltage, we observe Fermi level-dependent anomalous Hall conductance. As the Dirac point is approached from both electron and hole sides, the anomalous Hall conductance reaches 1/4 of the quantum anomalous Hall conductance 2e2/h. The exchange coupling strength is determined to be as high as 27 meV from the transition temperature of the induced magnetic phase. YIG/graphene/h-BN is an excellent heterostructure for demonstrating proximity-induced interactions in two-dimensional electron systems.