Control of Giant Topological Magnetic Moment and Valley Splitting in Trilayer Graphene

TL;DR

This study demonstrates that Bernal-stacked trilayer graphene exhibits large, tunable topological magnetic moments and valley splitting, enabling control of valley degeneracy through electric and magnetic fields for potential valleytronic applications.

Contribution

The paper reveals that ABA trilayer graphene hosts highly tunable topological magnetic moments with large valley g-factors, supported by combined experimental and theoretical analysis.

Findings

Valley g-factor reaches 1050 in ABA trilayer graphene.

Tunneling spectra match detailed theoretical models.

Electric and magnetic fields effectively control valley splitting.

Abstract

Bloch states of electrons in honeycomb two-dimensional crystals with multi-valley band structure and broken inversion symmetry have orbital magnetic moments of a topological nature. In crystals with two degenerate valleys, a perpendicular magnetic field lifts the valley degeneracy via a Zeeman effect due to these magnetic moments, leading to magnetoelectric effects which can be leveraged for creating valleytronic devices. In this work, we demonstrate that trilayer graphene with Bernal stacking, (ABA TLG) hosts topological magnetic moments with a large and widely tunable valley g-factor, reaching a value 1050 at the extreme of the studied parametric range. The reported experiment consists in sublattice-resolved scanning tunneling spectroscopy under perpendicular electric and magnetic fields that control the TLG bands. The tunneling spectra agree very well with the results of theoretical modeling that includes the full details of the TLG tight-binding model and accounts for a quantum-dot-like potential profile formed electrostatically under the scanning tunneling microscope tip.