In a study published in the Proceedings of the National Academy of Sciences, theoretical physicists at MIT explained how Jekyll-and-Hyde duality could emerge. They suggested that under specific conditions, a magnetic material's electrons could split into fractions of themselves to create quasiparticles called "anyons." In certain fractions, the quasiparticles should flow together without resistance, similar to how regular electrons can pair up to flow in conventional superconductors.
Over the past year, two separate experiments using different materials observed the same puzzling situation: the simultaneous presence of superconductivity and magnetism. Scientists had believed that these two quantum states were mutually exclusive; the existence of one should inherently eliminate the other.
If the team's scenario is accurate, it would introduce a completely new form of superconductivity, one that persists in the presence of magnetism and involves a supercurrent of exotic anyons instead of ordinary electrons.
Many more experiments are needed before one can declare victory. But this theory is very promising and shows that there can be new ways in which the phenomenon of superconductivity can arise.
Senthil Todadri, Study Lead Author and William and Emma Rogers Professor, Physics, MIT
Furthermore, if the concept of superconducting anyons can be verified and controlled in other materials, it could offer a new method to design stable qubits, atomic-scale "bits" that interact quantum mechanically to process information and perform complex computations much more efficiently than conventional computer bits.
“These theoretical ideas, if they pan out, could make this dream one tiny step within reach,” Todadri said.
The study’s co-author is MIT physics graduate student Zhengyan Darius Shi.
“Anything Goes”
Superconductivity and magnetism are macroscopic states that result from the behavior of electrons. A material is a magnet when electrons in its atomic structure have approximately the same spin, or orbital motion, generating a collective pull in the form of a magnetic field within the material as a whole.
A material is a superconductor when electrons passing through, in the form of voltage, can couple up in "Cooper pairs." In this paired state, electrons can move through a material without friction, rather than randomly colliding with its atomic latticework.
For many years, it was believed that superconductivity and magnetism should not coexist; superconductivity is a fragile state, and any magnetic field can easily break the bonds between Cooper pairs. But earlier this year, two separate experiments demonstrated otherwise.
In the first experiment, MIT's Long Ju and his colleagues discovered superconductivity and magnetism in rhombohedral graphene, a synthesized material made from four or five graphene layers.
It was electrifying. It set the place alive. And it introduced more questions as to how this could be possible.
Senthil Todadri, Study Lead Author and William and Emma Rogers Professor, Physics, MIT
Soon after, a second team reported similar dual states in the semiconducting crystal molybdenum ditelluride (MoTe2). Interestingly, the conditions in which MoTe2 becomes superconductive are the same conditions in which the material exhibits an exotic “fractional quantum anomalous Hall effect,” or FQAH, a phenomenon in which any electron passing through the material should split into fractions of itself. These fractional quasiparticles are known as “anyons.”
Anyons are fundamentally different from the two primary categories of particles that constitute the universe: bosons and fermions. Bosons are the sociable particle type, as they favor being together and moving in groups. The photon is the quintessential example of a boson.
Conversely, fermions prefer to be solitary and push away from each other if they get too close. Electrons, protons, and neutrons are examples of fermions. Collectively, bosons and fermions represent the two main particle classifications that form matter in the three-dimensional universe.
Anyons, by contrast, only exist in two-dimensional space. This third particle type was initially predicted in the 1980s, and its name was created by MIT’s Frank Wilczek, who intended it as a playful nod to the concept that, in terms of the particle's behavior, "anything goes."
Years after anyons were initially predicted, physicists, including Robert Laughlin, PhD ’79, Wilczek, and others, also proposed that, when magnetism is present, the quasiparticles ought to be able to superconduct.
People knew that magnetism was usually needed to get anyons to superconduct, and they looked for magnetism in many superconducting materials. But superconductivity and magnetism typically do not occur together. So, then they discarded the idea.
Senthil Todadri, Study Lead Author and William and Emma Rogers Professor, Physics, MIT
However, with the recent finding that the two states can, in reality, peacefully exist in specific materials, and especially in MoTe2, Todadri pondered: Could the old theory, and superconducting anyons, be relevant?
Moving Past Frustration
Todadri and Shi aimed to theoretically address that question, expanding on their recent research. In their new study, the team determined the conditions under which superconducting anyons could appear in a two-dimensional material.
To achieve this, they utilized quantum field theory equations, which explain how interactions at the quantum level, like individual anyons, can produce macroscopic quantum states, such as superconductivity. This undertaking was not straightforward, as anyons are known to be resistant to movement, let alone superconducting, together.
“When you have anyons in the system, what happens is each anyon may try to move, but it’s frustrated by the presence of other anyons,” Todadri details. “This frustration happens even if the anyons are extremely far away from each other. And that’s a purely quantum mechanical effect.”
Despite this, the team investigated scenarios where anyons could overcome this hindrance and behave as a single macroscopic fluid. Anyons arise when electrons split into fractional parts under specific conditions within two-dimensional, single-atom-thick materials like MoTe2. Researchers had previously noted that MoTe2 demonstrates the FQAH effect, where electrons fractionalize without an external magnetic field.
Todadri and Shi used MoTe2 as the foundation for their theoretical research. They simulated the conditions that lead to the FQAH phenomenon in MoTe2, and then analyzed how electrons would split and the types of anyons that would form as they theoretically increased the number of electrons in the material.
The researchers observed that, based on the material's electron density, two kinds of anyons can arise: anyons with either 1/3 or 2/3 the charge of an electron. They subsequently used quantum field theory equations to determine how each anyon type would interact.
They discovered that when the anyons are primarily of the 1/3 variety, they exhibit predictable frustration, and their motion results in standard metallic conduction.
However, when anyons are mostly of the 2/3 type, this specific fraction encourages the typically sluggish anyons to move together, forming a superconductor, akin to how electrons pair up and flow in traditional superconductors.
“These anyons break out of their frustration and can move without friction,” Todadri said. “The amazing thing is, this is an entirely different mechanism by which a superconductor can form, but in a way that can be described as Cooper pairs in any other system.”
Their research showed that superconducting anyons can arise at specific electron densities. Furthermore, they discovered that when superconducting anyons first appear, they do so in a completely novel pattern of swirling supercurrents that spontaneously manifest in random spots throughout the material.
This behavior differs from traditional superconductors and represents an exotic state that experimentalists can seek to validate the team's theory. If their theory is accurate, it would introduce a new type of superconductivity through the quantum interactions of anyons.
Todadri concludes, “If our anyon-based explanation is what is happening in MoTe2, it opens the door to the study of a new kind of quantum matter which may be called ‘anyonic quantum matter. This will be a new chapter in quantum physics.”
The study was funded, in part, by the National Science Foundation.
Journal Reference:
Shi, Z. D., & T. Senthil. (2025). Anyon delocalization transitions out of a disordered fractional quantum anomalous Hall insulator. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2520608122. https://www.pnas.org/doi/10.1073/pnas.2520608122.