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Researchers have shown that the magnetic order inside a layered semiconductor can shift the energy of light emitted by an exciton-polariton condensate. The material is chromium sulfide bromide (CrSBr). In the reported experiment, applying a magnetic field changes how its layers are magnetically arranged, and that change alters the color, meaning the energy, of the light the condensate emits. The work was reported in 2026 by the University of Regensburg and published as a Nature Materials paper led by first author Heng Zhang.
What the experiment did
The reported sequence has three stages. Each stage is described by the University of Regensburg report, which was published through Phys.org on October 8, 2026.
- Ultrashort laser pulses excite the structures, creating exciton-polaritons in the layered CrSBr.
- As the excitation builds, the system passes a condensation threshold. At that point the emitted light becomes far brighter and its waves begin to act in step.
- A magnetic field is applied to change the magnetic order of the material. The energy of the emitted light shifts as a result.
The full report is available at phys.org/news/2026-10-layered-semiconductor-magnetic-emitted-quantum. It is the main public account of the experiment used in this article.
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Exciton
An exciton is an electron and a hole (the absence of an electron) bound together inside a semiconductor. It is an excited state of the material, not a free particle, and it can release its energy as light.
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Exciton-polariton
When an exciton couples to light trapped in an optical resonator, the combined state is called an exciton-polariton. The report explains that the light part of the mixture reduces the effective mass of the particle. A lighter particle makes collective quantum behavior easier to reach, which is why polaritons are attractive for this kind of work.
Condensate
A condensate is a collective state in which many particles behave as one coherent entity. In this experiment the condensate is the source of the emitted light, so changes to the condensate show up directly in the light the system produces.
Why a layered magnet matters
CrSBr is built from atomically thin layers. Within each layer, the magnetic moments (the tiny magnetic orientations of the electrons’ spins) point in the same direction. Neighboring layers point in opposite directions. According to the report’s explanation, this arrangement confines excitons to their own layers.
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1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesThe report uses the phrase “magnetic cage” as an explanatory metaphor. It is a way of describing how the spin pattern holds the excitons in place. It does not refer to a physical cage built into the material.
Opposite spins in neighboring layers
The default pattern, with adjacent layers pointing opposite ways, is what keeps excitons separated by layer. That separation is part of the starting condition for the experiment, and the report presents it as the reason magnetic order can have a strong effect on the excitons.
Field-driven spin alignment
An external magnetic field can align the spins across layers. This changes the properties of the exciton-polaritons, including their energy. The field is therefore the control input and the magnetic order is the mechanism that carries its effect into the light.
How the team identified condensation
Condensation is hard to confirm by looking at one measurement alone, so the report relies on two observations taken together. The first is a sudden jump in brightness at a threshold. The second is coherence, meaning the light waves are ordered and oscillate in step.
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The report gives the following statement from first author Dr. Heng Zhang:
“Once the condensation threshold is reached, the intensity of the emitted light suddenly increases more than a hundredfold. At the same time, the light waves become ordered and, in a sense, oscillate in step with one another. This so-called coherence provides clear evidence of condensation,”
The “more than a hundredfold” figure is a measurement from this experiment, reported at the threshold. The coherence observation is what the team used to confirm that the state is a condensate and not just a bright emission.
The magnetic-control comparison
The most practical claim in the report concerns how large the effect is. Co-first author Christian Weidgans is quoted as saying:
“While previous approaches have relied, among other methods, on applying an electrical voltage, even moderate magnetic fields in CrSBr enable a shift in the energy of the emitted light that is up to 10 times larger. In this way, the quantum state can be controlled directly through the magnetism of the material.”
The “up to 10 times larger” comparison is the authors’ own figure, reported through the University of Regensburg account. It compares magnetic-field tuning in CrSBr with earlier approaches, including tuning by electrical voltage. The coverage available for this article does not state the field strengths, sample conditions or measurement setup behind that ratio, so treat it as a reported comparison rather than a standard benchmark.
What is demonstrated and what is still prospective
The report says the work creates an interface between extended quantum states and magnetic order. That interface is the demonstrated result: a magnetic field changes the energy of light from a condensate in this layered material.
Demonstrated in the reported experiment
- Magnetic order in CrSBr controls the energy of light emitted by an exciton-polariton condensate.
- The condensate shows a threshold-driven increase in emitted-light intensity and coherence, which the team uses as evidence of condensation.
Described as future opportunities, not achieved results
- Direct coupling of the light emitted by the condensate to magnetic states.
- Influence of microwaves on magnetic order.
- Integration with magnetic memory.
- Conversion between microwave and optical signals.
Co-first author Dr. Niloufar Nilforoushan describes the first of these directions:
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“In the future, the platform could be used to directly couple the light emitted by the condensate to magnetic states and manipulate it on extremely short time scales,”
The word “could” carries the weight here. The experiment shows the control; it does not show the coupling, microwave control, memory or conversion applications.
A separate CrSBr study for context
A different 2026 study of CrSBr is covered in a News & Views article in Light: Science & Applications. Konstantinos S. Daskalakis wrote the commentary, titled “A magnetic dial for exciton-polaritons,” on August 21, 2026. It discusses work by Li et al. on how magnetic fields tune the coupling strength and optical nonlinearity of exciton-polaritons in CrSBr. The commentary notes that the higher-energy exciton was more sensitive to interlayer spin order in that study.
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That study is not the condensate experiment described above. The two papers measure different things, so the table below keeps them apart.
| Item | Condensate experiment (University of Regensburg report, October 8, 2026) | Li et al. study (Daskalakis News & Views, August 21, 2026) |
|---|---|---|
| What magnetic order changes | Energy of light emitted by an exciton-polariton condensate | Exciton-polariton coupling strength and optical nonlinearity |
| Reported magnitude | Emitted-light intensity rises more than a hundredfold at threshold; energy shift described as up to 10 times larger than voltage-based approaches (Weidgans) | Rabi splitting of about 632 meV at 6 K and 745 meV at room temperature for a representative flake; a decrease of nearly 100 meV within a few tenths of a tesla |
| Temperature and field conditions | Not stated in the coverage available | Values given for 6 K and room temperature; the flake and field conditions are as reported in the commentary |
| Source | University of Regensburg, via Phys.org | Konstantinos S. Daskalakis, Light: Science & Applications News & Views |
Daskalakis summarizes the broader finding this way:
“Experiments in the van der Waals magnet CrSBr show that magnetic fields can strongly tune exciton-polariton coupling strength and optical nonlinearity.”
The commentary is available at nature.com/articles/s41377-026-02445-9.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Could this lead to quantum communication?
The reported work does not demonstrate quantum communication, and neither the Regensburg report nor the commentary claims it does. Readers may see the link drawn in other coverage, but the experiment itself shows a laboratory control effect. The distance between that result and a usable communication device is large. Any path would need the coupling, microwave and memory steps listed above to be shown first, and none of them is reported as achieved here.
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Limits of the available coverage
- The headline paper is listed as Heng Zhang et al., “Magnetic control of an exciton–polariton condensate in a van der Waals magnet,” Nature Materials (2026), DOI 10.1038/s41563-026-02751-y. The full text was not accessible when this article was prepared, so the methods, sample details, temperatures and measurement conditions for the condensate experiment are not described here.
- The “up to 10 times larger” figure and the “more than a hundredfold” intensity increase come from the university report and the quoted authors. Readers should check them against the paper once they can access it.
- The Li et al. numbers come from a commentary on a different study. They give context for CrSBr’s magnetic tuning but do not describe the condensate experiment.
The quotes in this article are taken directly from the University of Regensburg report and the Daskalakis commentary.
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