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Magnetoelectric Control of Helical Light Emission in a Moiré Chern Magnet

Eric Anderson1,*, Heonjoon Park1, Kaijie Yang2, Jiaqi Cai1, Takashi Taniguchi3, Kenji Watanabe4, Liang Fu5, Ting Cao2, Di Xiao2,1,† et al.

Xiaodong Xu1,2,‡

  • *Present address: Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies (C2N), Palaiseau 91120, France.
  • †Contact author: dixiao@uw.edu
  • ‡Contact author: xuxd@uw.edu
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Phys. Rev. X 15, 031057 – Published 27 August, 2025

DOI: https://doi.org/10.1103/ds5p-763x

Abstract

Magnetoelectric effects and their coupling to light helicity are important for both fundamental science and applications in sensing, communication, and data storage. Traditional approaches require complex device architectures, involving separate spin-injection, ferromagnetic, and optically active layers. Recently, the emergence of 2D semiconductor moiré superlattices with flat Chern bands and strong light-matter interactions has established a simple yet powerful platform for exploring the coupling between photon, electron, and spin degrees of freedom. Here, we report efficient current control of spontaneous ferromagnetism and associated helicity of light emission in moiré MoTe2 bilayer—a system which hosts a rich variety of topological phases, including newly discovered zero-field fractional Chern insulators. We show that the current control is effective over a wide range of doping of the first moiré Chern band, implying the uniformity of the Berry curvature distribution over the flat band. By setting the system into the anomalous Hall metal phase, a current as small as 10 nA is sufficient to switch the magnetic order, a substantial improvement over both conventional spin-torque architectures and other moiré systems. The realized current control of ferromagnetism leads to continuous tuning of trion photoluminescence helicity from left to right circular via spin-valley Hall torque at zero magnetic field. Our results pave the way for topological optospintronics based on semiconductors with synthetic flat Chern bands.

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Popular Summary

Creating systems where light, electricity, and magnetism are all strongly linked is a major goal in modern physics, with far-reaching implications for various quantum technologies. In this work, we demonstrate a new way to control both the magnetic behavior and the polarization of light emitted from a material known as twisted bilayer molybdenum ditelluride (tMoTe2). This material has gained a lot of attention because it hosts the fractional quantum anomalous Hall effect, in which conductance takes on quantized values that do not change with material imperfections, even under zero magnetic field. One especially exciting feature is its potential to support zero-field anyons, strange quantum particles that could be useful for building robust quantum computers. We achieve control of magnetism and polarization of emitted light in tMoTe2 using electrical current alone, improving on the efficiency of existing approaches by 4 orders of magnitude.

Using a suite of spatial- and polarization-resolved magneto-optical measurement techniques, we find that running an electrical current through tMoTe2 allows us to switch its magnetic state and, at the same time, continuously change the handedness (left- or right-circular polarization) of the emitted light. This happens efficiently because the material can be set into an anomalous Hall metal phase, where the electrons naturally tend to move in opposite directions depending on their internal quantum properties, like spin or valley (a property related to how electrons move in the crystal lattice). This movement subtly changes the magnetic and optical behavior of the device in a highly controllable way.

This result demonstrates a way to link magnetic memory and optical communication in a single device, controlled entirely by small electrical current. Even more intriguing is the potential to use this control to explore and manipulate anyons.

Article Text

Supplemental Material

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Phys. Rev. X 15, 031057– Published 27 August, 2025
  • Received 27 February 2025
  • Revised 23 June 2025
  • Accepted 22 July 2025
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