Riding the quantum wave: quasiparticles reveal a magneto-optical transport phenomenon
image: When a laser pulse strikes a material layer, excitons are generated and move through the layer as electron–hole pairs. Their motion is controlled and accelerated by the wave-like magnetic alignment of the spins (triangles) in the layers.
Credit: Kilian Neddermeyer
Excitons are being explored in materials science and information technology as a means of storing light. These luminous quasiparticles move through individual layers of quantum materials and can absorb and emit light with high efficiency. They form when a laser pulse excites an electron, leaving behind a positively charged “hole.” The electron and hole attract each other and behave together like a new, independent particle. When the quasiparticle recombines, it emits light and can be detected in high-tech laboratories.
Excitons in ultrathin quantum materials have been intensively studied for more than a decade, including by Alexey Chernikov and his team. At the Cluster of Excellence ctd.qmat—Complexity, Topology and Dynamics in Quantum Matter—at the Universities of Würzburg and Dresden, Chernikov and an international research team based in Dresden have now made a surprising discovery: excitons can be carried along by the magnetic excitations of a quantum material and, as a result, accelerated to ultrahigh speeds:
“The fact that the motion of optical particles can be controlled by magnetism is new. Until now, we only knew that the transport of electrons could be controlled by the magnetic order in a quantum material—this is how some sensors in smartphones work, for example. This newly discovered link between optics and magnetism could open up entirely new technological possibilities,” explains Florian Dirnberger, head of an Emmy Noether Junior Research Group at the Technical University of Munich and formerly a postdoctoral researcher in Alexey Chernikov’s Chair of Ultrafast Microscopy and Photonics, where he was responsible for carrying out the research project.
Spin Waves Enable Ultrafast Transport
The antiferromagnetic quantum semiconductor chromium sulfide bromide (CrSBr) becomes magnetic at −141.15° Celsius. At this temperature, the electrons inside the material begin to oscillate and attempt to align in parallel. The material under investigation consists of two independent, ultrathin layers. The alignment of the magnetic moments—known as spins—varies from one layer to the next. “When we excite the cooled material with a laser pulse, the electron spins begin to oscillate and propagate outward in waves—like ripples created when a stone is thrown into a lake,” explains Sophia Terres, a doctoral researcher in Alexey Chernikov’s group and co-responsible for the experiments.
When the team examined the quantum material using highly sensitive spectroscopy in a high-tech laboratory, they made a remarkable discovery. Instead of moving randomly, as is usually the case, the excitons were carried along by the spin waves. “The luminous quasiparticles effectively ride on the spin waves, accelerating them dramatically. We have never observed exciton motion this fast before,” says Terres.
Although it was only about five years ago that excitons were first observed in the antiferromagnetic semiconductor CrSBr, the present study demonstrates an additional, entirely novel phenomenon: the transport of excitons depends on the magnetic order of the material. This relationship has now been demonstrated for the first time in a quantum material by the ctd.qmat team.
Magneto-Optics Becomes a Reality
The experimental findings by Chernikov and his team could pave the way for magneto-optical quantum technologies. To date, electromagnetic applications have been the standard in industry, electronics, communications, and mobility. If optical excitations—such as excitons—can be controlled magnetically, this could open up new possibilities for hybrid technologies. “Circuits based on light are faster and transmit information with fewer losses than current technologies,” explains Dirnberger. “We now know that optical components could also be controlled magnetically. This is an exciting new prospect for future technologies and could give spintronics a significant boost in the coming years.”
Illustration
YouTube (with music): https://youtu.be/Evl4EoWuE2I
Quasiparticles ride magnetic waves: When a laser pulse strikes a material layer, excitons are generated and move through the layer as electron–hole pairs. Their motion is controlled and accelerated by the wave-like magnetic alignment of the spins (triangles) in the layers.
Publication
Exciton transport driven by spin excitations in an antiferromagnet; Florian Dirnberger, Sophia Terres, Zakhar A. Iakovlev, Kseniia Mosina, Zdenek Sofer, Akashdeep Kamra, Mikhail M. Glazov & Alexey Chernikov; Nature Nanotechnology 21, 65–70 (2026), https://doi.org/10.1038/s41565-025-02068-y.
ctd.qmat
The Cluster of Excellence ctd.qmat — Complexity, Topology and Dynamics in Quantum Matter — at Julius-Maximilians-Universität Würzburg and TUD Dresden University of Technology explores and develops novel quantum materials with tailored properties. Around 300 researchers from over 30 countries work at the interface of physics, chemistry, and materials science to lay the foundations for tomorrow’s technologies. In 2026, the cluster entered the second funding period of the German Excellence Strategy of the Federal and State Governments — with an expanded focus on the dynamics of quantum processes.
Contact
Prof. Alexey Chernikov
Chair of Ultrafast Microscopy and Photonics
TUD Dresden University of Technology
Tel: +49 351 463-336439
Email: alexey.chernikov@tu-dresden.de
Katja Lesser
Press Officer & Head of Communications
Exzellenzcluster ctd.qmat
Tel: +49 351 463-33496
Email: katja.lesser@tu-dresden.de