In a breakthrough that could transform the understanding of quantum magnetism, scientists have shown that a spinon, which was once believed to exist only in pairs, can travel alone.
The discovery further enhances understanding of magnetism and could help pave the way for future technologies, including quantum computers and advanced magnetic materials.
When spin flips ripple
Spinons are quasiparticles that arise as quantum disturbances behaving like individual particles within magnetic systems.
They emerge in low-dimensional quantum materials, particularly in one-dimensional (1D) spin chains, where electrons are arranged in a linear sequence and interact through their quantum spins.
In such systems, flipping a single spin doesn’t just affect one electron; it creates a ripple across the chain. This ripple can act as a discrete entity, carrying a spin value of ½. That entity is the spinon.
Today, magnets are central to a wide range of technologies, including computer memory, speakers, electric motors, and medical imaging devices.
The idea of spinons dates back to the early 1980s, when physicists Ludwig Faddeev and Leon Takhtajan proposed that a spin-1 excitation in certain quantum models could fractionalize into two spin-½ excitations.
These were named spinons, which are considered exotic because they behave as if an indivisible quantum of spin has split into two.
However, all experimental observations until now had detected spinons only in pairs, reinforcing the belief that they could not exist independently.
That assumption has now been challenged.
One spin to rule
In a new theoretical study, physicists from the University of Warsaw and the University of British Columbia showed how to isolate a lone spinon using a well-known model of quantum magnetism, the Heisenberg spin-½ chain.
By adding a single spin to this system, either in its ground state or in a simplified model known as the valence-bond solid (VBS), they demonstrated how a single unpaired spin can move freely through the spin chain, acting as a solitary spinon.
What makes the finding more impactful is that it’s not purely theoretical. A recent experiment led by C. Zhao and published in Nature Materials observed spin-½ excitations in nanographene-based antiferromagnetic chains that reflect the lone spinon behavior described in the study.
This experimental validation confirms that the phenomenon can occur in real quantum materials, not just in simulations.
Understanding how a single spinon can exist has far-reaching implications. Spinons are closely linked to quantum entanglement, a core principle of quantum computing and quantum information science.
They’re also involved in exotic states of matter like high-temperature superconductors and quantum spin liquids.
By gaining better control over spinon dynamics, scientists could open new pathways for developing advanced magnetic materials and potentially qubit systems for quantum computers.
“Our research not only deepens our knowledge of magnets, but can also have far-reaching consequences in other areas of physics and technology”, said Prof Krzysztof Wohlfeld of the Faculty of Physics at the University of Warsaw.
The study was published in the journal Physical Review Letters.