The material at the heart of the study is chromium thiophosphate, CrPS4, an air-stable, layered magnetic semiconductor that has become a workhorse of two-dimensional magnetism research. On its own, CrPS4 behaves conventionally depending on thickness: few-layer samples can show ferromagnetic order, while bulk crystals adopt an antiferromagnetic arrangement. Neither of these ground states, however, exhibits the hallmark of altermagnetism, which is a finite splitting between electronic states of opposite spin that does not arise from spin-orbit coupling but instead from the symmetry of the crystal and its magnetic arrangement. The researchers reasoned that if two CrPS4 flakes were stacked with their crystal axes rotated by ninety degrees, the interlayer symmetry would be altered in precisely the way theory predicts should generate an altermagnetic state.

The idea traces back to theoretical work suggesting that twisted magnetic van der Waals bilayers constitute an ideal platform for altermagnetism. In an ordinary antiferromagnet, time-reversal symmetry combined with a lattice translation protects the degeneracy of spin-up and spin-down bands, so the electronic structure shows no net spin splitting. When layers are rotated relative to one another, that combined symmetry operation is broken, and the spin degeneracy is lifted in a momentum-dependent fashion. The result is a material whose spins cancel macroscopically, avoiding the stray fields that plague ferromagnetic devices, yet whose electronic bands are split in a way that can carry spin-polarized currents. For spintronics, this combination is extraordinarily attractive: fast switching, dense packing, and robust spin information without the crosstalk that limits conventional magnetic memory.

To test the prediction, the team fabricated orthogonally twisted CrPS4/CrPS4 homostructures, stacking four-layer flakes rotated by ninety degrees relative to each other. They then interrogated the samples with a battery of optical probes, beginning with polarized Raman spectroscopy. In the twisted configuration, the Raman spectra revealed a splitting of phonon modes that is absent in untwisted controls. This vibrational fingerprint, the researchers show, arises from the interlayer coupling unique to the altermagnetic arrangement: the same symmetry breaking that splits the electronic bands also modifies the lattice dynamics, producing a spectroscopic signature that distinguishes the twisted state from any simple superposition of ferromagnetic and antiferromagnetic layers.

The more decisive evidence came from magneto-optical spectroscopy. Measuring the photoluminescence of the twisted homostructure under an applied magnetic field, the researchers tracked the degree of circular polarization of the emitted light. The twisted sample displayed a magnetic-field dependence that resembles the response of a ferromagnet, a striking result given that the underlying spin order is compensated. Even more telling was the observation of a pronounced Zeeman splitting in the photoluminescence spectra, with the sigma-plus and sigma-minus emission peaks separating as the field increased. Crucially, neither ferromagnetic nor antiferromagnetic CrPS4 samples show this splitting in the same configuration. Its emergence only in the twisted geometry indicates that the stack has entered a genuinely distinct magnetic ground state, one that carries the fingerprints of altermagnetism.

First-principles calculations reinforced the interpretation. Using density functional theory with an on-site Coulomb correction to treat the correlated chromium d electrons, the team computed the electronic structure of the orthogonally twisted bilayer and found large spin-split bands in an antiferromagnetic configuration. The pattern of the splitting matches the theoretical expectations for altermagnets: opposite-spin bands separate in momentum space in a way dictated by crystal rotation symmetry, while the net magnetization remains zero. The agreement between the computed band structure and the optical measurements provides a coherent picture in which twisting acts as a symmetry-breaking knob that switches on spin splitting without introducing any net magnetic moment.

The significance of the result extends beyond confirming a theoretical prediction. Van der Waals homostructures, in which the same material is stacked with controlled twist angles, have already revolutionized research on graphene and transition metal dichalcogenides, giving rise to moiré physics, flat bands, and correlated electronic phases. The present work shows that the same stacking engineering can serve as a design principle for magnetism itself. Rather than searching for new chemical compounds that happen to be altermagnets, researchers can now, in principle, manufacture altermagnetic states from well-characterized magnetic layers by choosing the twist angle. Because the twist angle is a continuously tunable parameter, it opens a route to systematically exploring how altermagnetic spin splitting evolves with interlayer symmetry, something no fixed crystal structure can offer.

The experimental signatures reported here also add to a growing toolbox for identifying altermagnets. Earlier confirmations of altermagnetic band splitting relied on techniques such as spin-resolved and angle-resolved photoemission spectroscopy, x-ray magnetic circular dichroism, and magneto-optical Kerr effect measurements in compounds like CrSb, MnTe, and RuO2. The CrPS4 study demonstrates that circularly polarized photoluminescence and Raman spectroscopy, both accessible table-top optical methods, can detect altermagnetism in atomically thin devices. This accessibility matters: optical probes can be applied to microscopic samples inside cryostats, under magnetic fields, and across device geometries, accelerating the pace at which candidate altermagnetic structures can be screened and characterized.

For applications, the appeal of altermagnets lies in their potential to combine the speed and stability of antiferromagnetic spintronics with the readout convenience of ferromagnets. Antiferromagnetic memory elements are immune to external fields and can in principle switch at terahertz frequencies, but their vanishing net moment makes them hard to read. Altermagnets solve the readout problem because their spin-split bands allow spin-polarized transport and magneto-optical signals even without net magnetization. A twisted van der Waals altermagnet adds another dimension: the state exists in an atomically thin, air-stable semiconductor that can be integrated into heterostructures with other two-dimensional materials, potentially enabling spin filters, tunnel junctions, and valleytronic devices in which spin and momentum are locked by design.

Challenges remain before such devices materialize. The reported signatures are spectroscopic rather than transport-based, and future work will need to demonstrate electrical readout and manipulation of the altermagnetic state, quantify the magnitude and temperature stability of the spin splitting, and explore how different twist angles and layer numbers tune the effect. Still, the demonstration that a simple ninety-degree rotation of identical CrPS4 flakes produces a magnetic phase absent from either constituent marks a conceptual milestone. It establishes twisted van der Waals homostructures as an experimental platform for altermagnetism, transforming a theoretical proposal into a tangible, measurable state of matter and handing the spintronics community a new material class to engineer.

Subject of Research: Experimental observation of altermagnetism in orthogonally twisted CrPS4 van der Waals homostructures

Article Title: Altermagnetism in twisted van der Waals homostructures

Article References: Chen, J., Xie, X., Li, S., Zhang, S., Hou, S., Zhang, X., He, J., Liu, Z., Wang, J.-T., & Liu, Y. (2026). Altermagnetism in twisted van der Waals homostructures. Nature Physics. https://doi.org/10.1038/s41567-026-03440-y

Image Credits: AI Generated

DOI: 10.1038/s41567-026-03440-y

Keywords: altermagnetism, CrPS4, van der Waals heterostructures, twisted bilayers, spintronics, magneto-optical spectroscopy, Zeeman splitting, Raman spectroscopy, 2D magnets, spin splitting, antiferromagnetism, first-principles calculations

The central challenge addressed by the work is deeply rooted in magnetic symmetry. In an altermagnet, magnetic moments on different atomic sites can cancel in the conventional sense while still producing a momentum-dependent spin splitting in the electronic band structure. This unusual arrangement gives altermagnets characteristics that are distinct from both ordinary ferromagnets and conventional antiferromagnets. However, when the magnetic order points perpendicular to the material plane, the symmetry of the system can make it extremely difficult to read electrically. A conventional Hall signal, for example, is usually associated with a net magnetization, while an ideally compensated magnetic structure produces no obvious macroscopic magnetic moment. That limitation has hindered experiments designed to probe and control perpendicular altermagnetic states.

The new strategy relies on placing the altermagnet CrSb next to PtTe₂, a Dirac semimetal with unusual electronic properties. A Dirac semimetal is a material in which the energy bands can meet at special points or regions in momentum space, allowing charge carriers to behave in ways that resemble relativistic particles. These electronic states are highly sensitive to symmetry, interfaces and magnetic proximity effects. By growing PtTe₂ and CrSb together in an engineered heterostructure, the researchers created an interface where the electronic structure of the nonmagnetic or weakly magnetic component can be influenced by the altermagnetic order in CrSb. This interfacial coupling provides a route for converting an otherwise difficult-to-detect magnetic configuration into an electrical signal.

That conversion is described as an anomalous Hall read-out generated by the altermagnetic proximity effect. The anomalous Hall effect occurs when charge carriers traveling through a material are deflected sideways by mechanisms linked to broken time-reversal symmetry and spin–orbit coupling. In a conventional ferromagnet, the effect is often connected to the material’s magnetization. In the PtTe₂/CrSb system, however, the signal provides access to the magnetic order of CrSb even though the altermagnet is magnetically compensated. The proximity effect effectively transfers information about the Néel vector—the direction describing the arrangement of the opposing magnetic sublattices—into the electronic transport response of the adjacent Dirac semimetal. This gives researchers an electrical window into a magnetic state that is otherwise difficult to observe directly.

The distinction between magnetization and the Néel vector is essential for understanding why the advance matters. In a ferromagnet, switching the magnetization reverses a net magnetic moment, making the state relatively straightforward to detect with electrical, optical or magnetic probes. In an antiferromagnet or altermagnet, the relevant order parameter is instead the orientation of the sublattice moments. The Néel vector can change direction without producing a large overall magnetic field, which is attractive for dense device architectures because neighboring elements are less likely to disturb one another. At the same time, this compensation makes the order harder to manipulate and measure. The PtTe₂/CrSb interface addresses both sides of this problem by coupling the hidden magnetic orientation to charge transport and to current-induced torques.

The researchers also demonstrate electrical control through spin–orbit torque. When an electrical current flows through a material with strong spin–orbit coupling, the interaction between an electron’s motion and its spin can generate a nonequilibrium spin accumulation or spin current. When that spin angular momentum reaches a neighboring magnetic layer, it can exert a torque on the magnetic order. In the heterostructure, this mechanism provides an electrically generated force capable of manipulating the epitaxial perpendicular Néel vector in CrSb. The term “epitaxial” indicates that the layers are arranged with a defined crystallographic relationship, rather than being randomly oriented. Such structural order is important because altermagnetic properties depend strongly on crystal symmetry and on the precise direction of the magnetic axis.

Deterministic switching is particularly significant because it means the electrical stimulus can reliably select between distinct magnetic states rather than merely disturbing or randomly reorienting the order. For a memory device, a readable and repeatable switching pathway is indispensable. The combination reported here—an anomalous Hall signal for read-out and spin–orbit torque for writing—resembles the basic operating logic of modern magnetic memory, while using a compensated magnetic order parameter instead of a conventional ferromagnetic magnetization. If the approach can be integrated into scalable device geometries, it could offer a route toward memory elements that are compact, fast and resistant to unwanted magnetic cross-talk.

The PtTe₂/CrSb design also illustrates why heterostructures are becoming central to altermagnet research. A single material may possess remarkable magnetic symmetry but lack an efficient electrical interface for reading or switching it. Combining materials allows each layer to perform a different function: CrSb supplies the perpendicular altermagnetic order, while PtTe₂ contributes a Dirac electronic structure and strong spin–orbit physics that can translate electrical currents into magnetic control signals. The interface is therefore not merely a boundary between two crystals; it is an active functional region where magnetic symmetry, band structure and angular momentum transport become interconnected. This approach could be extended to other combinations of altermagnets, semimetals and spin–orbit materials.

The findings arrive as researchers worldwide search for alternatives to conventional magnetic memory and logic. Ferromagnetic devices are mature, but their stray fields, energy costs and scaling limits motivate the development of compensated magnetic systems. Altermagnets are especially appealing because they may combine the stability and low stray-field behavior associated with antiferromagnets with the spin-polarized transport phenomena more commonly associated with ferromagnets. The reported electrical reading and deterministic switching of perpendicular order directly confront two of the field’s most important practical barriers. Although further work will be needed to establish operating speeds, endurance, energy efficiency, thermal stability and fabrication compatibility, the PtTe₂/CrSb platform provides a concrete device-oriented framework for evaluating those questions.

More broadly, the study demonstrates how controlling symmetry can be just as important as selecting a magnetic material. The researchers did not simply seek a stronger magnetic signal; they engineered an interface that makes a symmetry-hidden order parameter visible and controllable through electricity. That conceptual shift could influence the design of future spintronic systems, in which information is encoded not only in magnetization but also in the orientation of compensated magnetic sublattices and in momentum-dependent spin textures. By showing that perpendicular altermagnetic order can be both detected and switched, the work expands the functional possibilities of altermagnetic heterostructures and brings the prospect of scalable altermagnetic memory closer to experimental reality.

Subject of Research: Electrical detection and deterministic switching of perpendicular altermagnetic order in a PtTe₂/CrSb heterostructure

Article Title: Electrical manipulation and detection of perpendicular altermagnetic order via a proximitized Dirac semimetal

Article References: Li, Z., He, W., Bai, H. et al. Electrical manipulation and detection of perpendicular altermagnetic order via a proximitized Dirac semimetal. Nat. Mater. (2026). https://doi.org/10.1038/s41563-026-02721-4

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41563-026-02721-4

Keywords: altermagnetism, spintronics, Dirac semimetal, PtTe₂, CrSb, anomalous Hall effect, spin–orbit torque, Néel vector, magnetic memory, magnetic heterostructures