Giant orbital Zeeman effects in a magnetic topological van der Waals interphase

TL;DR

This paper reports giant orbital Zeeman effects at a magnetic van der Waals interface, revealing a magnetic interphase with highly tunable properties, supported by spectroscopic evidence, theoretical calculations, and electrostatic modeling.

Contribution

It provides the first spectroscopic evidence of a magnetic interphase in vdW heterostructures with giant Zeeman effects and demonstrates tunability via tip gating.

Findings

Landé g-factors up to 230 observed at the interface

Giant asymmetric level splitting caused by orbital moments

Interface dipole and Zeeman effect tunable by tip gating

Abstract

Van der Waals (vdW) heterostructures allow the engineering of electronic and magnetic properties by the stacking different two-dimensional vdW materials. For example, orbital hybridisation and charge transfer at a vdW interface may result in electric fields across the interface that give rise to Rashba spin-orbit coupling. In magnetic vdW heterostructures, this in turn can drive the Dzyaloshinskii-Moriya interaction which leads to a canting of local magnetic moments at the vdW interface and may thus stabilise novel 2D magnetic phases. While such emergent magnetic "interphases" offer a promising platform for spin-based electronics, direct spectroscopic evidence for them is still lacking. Here, we report Zeeman effects with Land\'e $g$-factors up to $\approx230$ at the interface of graphene and the vdW ferromagnet Fe$_3$GeTe$_2$. They arise from a magnetic interphase in which local-moment canting and itinerant orbital moments generated by the non-trivial band topology of Fe$_3$GeTe$_2$ conspire to cause a giant asymmetric level splitting when a magnetic field is applied. Exploiting the inelastic phonon gap of graphene, we can directly access the buried vdW interface to the Fe$_3$GeTe$_2$ by scanning tunnelling spectroscopy. Systematically analyzing the Faraday-like screening of the tip electric field by the graphene, we demonstrate the tunability of the constitutional interface dipole, as well as the Zeeman effect, by tip gating. Our findings are supported by density functional theory and electrostatic modelling.