Voltage-Driven Atomic Sliding Flips Magnetism On and Off in Tetralayer Graphene

In a result that could reshape how physicists think about building magnetic devices from carbon alone, researchers at Cornell University and collaborating institutions have shown that a simple gate voltage can shove entire atomic layers of graphene sideways, toggling the material between a magnet and a non-magnet without any magnetic field, magnetic impurity, or permanent structural damage. The study, published in Nature Nanotechnology, demonstrates a non-volatile, reversible switch between two fundamentally different electronic phases in a four-layer graphene device, driven purely by the electrostatic force that a gate exerts on the carbon sheets. Because the memory of which state the device occupies persists after the voltage is removed, the work points toward a striking possibility: magnetism written, erased, and rewritten in a material made of nothing but carbon, using the same kind of electrical gating that already underpins conventional semiconductor electronics.

The physics at the heart of the experiment concerns stacking order. When graphene sheets are stacked, each successive layer can sit in slightly different registries relative to the layer beneath it. In the most common configuration, known as Bernal stacking, alternate layers align in a pattern that gives the material an ordinary, semimetallic electronic structure. A second arrangement, rhombohedral stacking, shifts each layer by the same registry offset in sequence, producing a dramatically different electronic landscape. Rhombohedral multilayer graphene has emerged in recent years as one of the richest platforms in condensed matter physics, hosting superconductivity, orbital ferromagnetism, and exotic topological states that are entirely absent in Bernal-stacked samples of the same thickness. The catch is that rhombohedral stacking is metastable, and growing devices in which the desired stacking is stable and well controlled has been a persistent challenge.

The Cornell team, led by corresponding author Kenji Yasuda, took advantage of the fact that these two stacking arrangements can be converted into one another by sliding entire layers laterally across each other. Because the layers in graphene are held together only by weak van der Waals forces, the energy barrier between registries is small enough that an electric field, and the carrier density it induces, can tip the balance. Earlier work by other groups had shown that doping and electric fields can influence stacking transitions in few-layer graphene, and that interlayer sliding in van der Waals materials can produce ferroelectric-like switching of polarization. What distinguishes the new study is the demonstration that this structural sliding transition can be harnessed as a non-volatile toggle for a collective magnetic phase, converting a structural degree of freedom into magnetic functionality.

Experimentally, the researchers fabricated devices from marginally twisted double-bilayer graphene, effectively four carbon layers held between top and bottom gates in a dual-gated Hall bar geometry. In such a device, sweeping the carrier density n and the displacement field D gives experimenters two independent knobs: n controls how many electrons or holes populate the layers, while D controls how asymmetrically charge is distributed between the top and bottom of the stack. By measuring longitudinal resistance as the gates were swept forward and backward, the team observed clear bistable switching between a Bernal-dominant configuration and a mixed state containing both rhombohedral and Bernal domains. The hysteresis in the resistance indicates a first-order structural phase transition: rather than sliding smoothly, the layers snap between registries, retaining whichever state they were last driven into until a sufficiently different gate condition pushes them back.

The phase diagram the team mapped out is remarkably broad, with the bistable switching persisting across a wide swath of the carrier density and displacement field plane. Quantum oscillation measurements confirmed the structural interpretation. In regions of the device identified as Bernal-dominant, Landau fan diagrams aligned with the known spectrum of Bernal tetralayer graphene, while the mixed regions displayed blurred oscillations consistent with a nearly equal coexistence of rhombohedral and Bernal domains. Strikingly, the hysteresis in the longitudinal resistance persisted all the way up to room temperature, indicating that the structural transition itself is robust and does not rely on cryogenic conditions. The magnetic phase that emerges from it, however, lives at much lower temperatures, with a Curie temperature of around 8 kelvin in parts of the phase space and closer to 2 kelvin elsewhere.

That magnetic phase is the central discovery. When the device is in the rhombohedral-Bernal mixed state, low-temperature transport measurements reveal an anomalous Hall effect: a transverse voltage that appears even at zero external magnetic field and shows hysteresis under magnetic field sweeps, the classic fingerprint of ferromagnetism. When the device is switched back into the Bernal-dominant state, the anomalous Hall signal vanishes. The authors demonstrated that this switching between magnet and non-magnet is non-volatile and repeatable: by cycling the gate voltages through the same sequence, they could repeatedly write and erase the ferromagnetic phase at a fixed set of gate values, with the state of the device determined entirely by its sweep history. The magnitude of the anomalous Hall signal stayed roughly consistent across cycles, although the coercive field varied between sweeps, a variability the authors attribute to the small magnetic energy scale of the ferromagnetism in their sample.

One of the most intriguing technical observations concerns the origin of the Hall signal itself. When the researchers applied opposite displacement fields, the sign of the anomalous Hall response reversed. This behavior led the authors to suggest that the Hall signal may originate not from the bulk of the rhombohedral regions but from the domain boundaries where Bernal and rhombohedral regions meet. Such boundaries are known in the graphene literature to host interesting electronic behavior, including topological valley transport, and in this system they may act as the conduits through which the ferromagnetic order produces its anomalous Hall response. Understanding exactly how domain walls between stacking regimes carry or mediate magnetic order is one of the questions the work leaves open, and the authors note that a full accounting of the resistance changes tied to domain configuration will require simultaneous real-space imaging and transport measurements.

The broader significance of the result lies in its demonstration that structural phase transitions in two-dimensional materials can serve as an on-demand control mechanism for complex electronic phases. In conventional phase-change materials, structural switching is used for memory applications, but the phases involved are typically distinguished by resistivity rather than by magnetism. In two-dimensional magnets such as chromium triiodide, pressure and strain have been shown to tune magnetic order, but those materials require magnetic atoms to exist in the first place. The graphene device here achieves magnetic switching in an elementally pure carbon system, where the magnetism is an emergent consequence of correlated electron behavior in a particular stacking arrangement. This decouples the magnetic functionality from any specific magnetic element and ties it instead to geometry, which can be manipulated electrically with van der Waals sliding.

There are, of course, substantial gaps between a low-temperature laboratory device and a practical technology. The ferromagnetic phase survives only at a few kelvin, the coercive fields fluctuate from cycle to cycle, and the domain configurations that underlie the switching appear to vary between preparations, producing scan-to-scan scatter in the hysteresis. Yet the structural switching itself endures to room temperature, and the strategy of using gate-induced sliding as a first-order transition between competing stacking polytypes is applicable in principle to other van der Waals materials where stacking governs exotic phases. As research into rhombohedral graphene continues to reveal superconductivity, fractional Chern insulators, and chiral superconducting candidates, the ability to switch between stacking regimes without rebuilding the device offers a new dimension of control. For now, the Cornell experiment stands as a vivid proof of concept: atoms slid by an electric field can turn a carbon crystal into a magnet, and back again, on command.

Subject of Research: Gate-induced layer sliding and stacking-order control of non-volatile magnetic switching in tetralayer graphene

Article Title: Gate-induced layer sliding drives non-volatile switching of magnetism in tetralayer graphene

Article References: Gate-induced layer sliding drives non-volatile switching of magnetism in tetralayer graphene. (n.d.). https://doi.org/10.1038/s41565-026-02306-x

Image Credits: AI Generated

DOI: 10.1038/s41565-026-02306-x

Keywords: graphene, layer sliding, rhombohedral stacking, Bernal stacking, ferromagnetism, anomalous Hall effect, non-volatile switching, two-dimensional materials, van der Waals, gate voltage, phase transition, stacking domains