Giant orbital Zeeman effects in a magnetic topological van der Waals interphase

In the world of modern electronics, scientists are constantly searching for ways to make devices smaller, faster, and more energy-efficient. A major frontier in this quest involves the study of materials that are only a few atoms thick, known as two-dimensional materials. Among these, a special class called topological materials has captured the imagination of researchers. These materials possess a unique internal structure where electrons move in a highly organized, protected way, almost as if they are flowing through a highway that cannot be easily blocked. When scientists combine these topological materials with magnets, they create a playground where the flow of electricity and the direction of magnetic spins can be manipulated in exotic ways. The goal is to harness these properties to build new types of computers that use the spin of electrons rather than just their charge, a field known as spintronics. However, while the theory behind these materials is rich and promising, finding direct proof of how they behave when stacked together in real devices has been difficult. The interface where two different materials meet often holds the key to new physics, but observing what happens in that tiny, buried space without disturbing it has remained a significant challenge.

A team of researchers has now peered directly into this hidden world, uncovering a surprising and powerful effect at the junction between two specific materials: a single layer of carbon atoms arranged in a honeycomb pattern, known as graphene, and a magnetic crystal called Fe3GeTe2. By stacking these two materials on top of each other, they created a van der Waals heterostructure, a sandwich held together by weak forces rather than strong chemical bonds. Using a highly sensitive microscope that can measure the flow of electricity at the atomic scale, the scientists observed something extraordinary. When they applied a magnetic field, the energy levels of the electrons at the interface split apart in a way that was far more dramatic than anyone expected. The magnitude of this splitting was so large that it corresponded to a magnetic response factor, known as the Landé g-factor, of approximately 230. For context, the standard magnetic response of a single electron is just 2. This means the electrons at this interface are reacting to the magnetic field more than one hundred times more strongly than a normal electron would.

The researchers discovered that this giant effect is not caused by a single mechanism but by a complex interplay of two different types of orbital motion. First, the unique electronic structure of the magnetic crystal creates a natural tendency for electrons to orbit in a specific way, generating a magnetic moment. Second, and perhaps more surprisingly, the interface itself creates a tilted arrangement of the magnetic spins within the crystal. This tilt, caused by the electric field that naturally exists where the two materials meet, forces the electrons to twist as they move, creating a chiral, or handed, orbital motion. It is the combination of these two effects—the natural orbital motion of the material and the twisting motion induced by the tilted magnetic spins—that produces the massive signal. The team was able to confirm that this phenomenon is specific to the interface, as the same effect was not seen when they tested the magnetic material alone or when they tested the graphene alone.

A crucial part of this discovery was the ability to control the effect with electricity. The researchers found that by adjusting the distance between their microscope probe and the sample, they could change the electric field at the interface. This adjustment allowed them to tune the strength of the magnetic response, effectively turning the giant effect up or down. This tunability is significant because it suggests that the magnetic properties of such a device could be controlled by simple electrical gates, without the need for large external magnets. The study also ruled out other potential explanations for the observed signals, such as the formation of tiny magnetic islands or the influence of the graphene's own electronic structure, confirming that the effect is a genuine property of the interface between the two materials.

The findings offer a new window into how magnetic and electronic properties can be engineered at the atomic scale. By demonstrating that the magnetic response at an interface can be both giant and electrically controllable, the work provides a concrete example of how topological and magnetic materials can be combined to create novel functionalities. The researchers suggest that this approach could open the door to new types of electronic components where information is stored and processed using the orbital motion of electrons, a field sometimes called orbitronics. While the immediate application of these findings is still in the realm of fundamental science, the ability to manipulate such strong magnetic effects with simple electric fields represents a promising step toward the next generation of spin-based technologies. The work stands as a clear demonstration that the interface between two simple materials can give rise to complex and powerful new behaviors that are not present in either material on its own.