Quantum Breakthrough: Physicists Discover “Lonely” Spinon That Defies Magnetic Norms

A new discovery reveals how a mysterious quantum spin excitation — a solitary spinon — can exist alone, hinting at advances in quantum technologies.

Scientists from the Faculty of Physics at the University of Warsaw and the University of British Columbia have identified a way for a “lone spinon” to form within magnetic systems. This unusual quantum particle represents a single, unpaired spin and its existence offers new insights into how magnetism works on a fundamental level. The breakthrough, which could eventually support the advancement of quantum computing and new types of magnetic materials, was detailed in the journal Physical Review Letters.

Human knowledge of magnetism dates back to ancient times, beginning with the discovery of naturally magnetized magnetite. This early curiosity quickly led to practical tools. By the 11th century, Chinese inventors had developed the first compasses, which revolutionized navigation. Today, magnets are integral to countless modern devices, including data storage systems, loudspeakers, electric motors, and even medical imaging technologies. Curiously, they have also become a staple of travel memorabilia, often displayed proudly on refrigerators alongside photographs.

Magnets and quantum mechanics

Despite its widespread use, the nature of magnetism remained incompletely understood for a long time. The situation became further complicated when Niels Bohr and Hendrika Johanna van Leeuwen showed that magnetism could not be explained within the framework of classical physics. It was not until the development of quantum mechanics in the 1920s that it was understood that the magnetic properties of matter are primarily due to interactions between the spins of electrons. Spin, along with mass and electric charge, is one of the fundamental properties of elementary particles.

In 1931, Hans Bethe proposed a mathematically elegant solution to one of the fundamental quantum models of magnetism — the so-called one-dimensional Heisenberg model. Less than half a century later, in 1981, Ludwig Faddeev and Leon Takhtajan realized that the solutions to this model exhibited a surprising phenomenon: as if an indivisible electron “splits” into two more fundamental particles. The spin of the electron is 1/2 (in units of Planck’s constant ħ) and can be oriented in any direction in space. In the standard situation, an excitation involves the reversal of the spin of one electron, resulting in a change in the spin of the whole system by 1.

However, from Faddeev and Takhtajan’s theory, it follows that the fundamental excitations in a magnet change the total spin of the system by 1/2. These exotically behaving excitations were named spinons. Since then, many experiments have confirmed their existence. However, it was long believed that spinons could only form in pairs — and indeed, they had always been observed in this form — which made the phenomenon seem somewhat less “exotic.”

A lone spinon

In a paper just published in Physical Review Letters, a team of scientists from the Faculty of Physics at the University of Warsaw and the University of British Columbia has shown how such a singular excitation can be created as a single spinon. Such a spinon can be created in a very simple way: it is enough to add one extra spin to the ground state of the one-dimensional Heisenberg model (a theoretical description of a number of interacting spins).

The researchers also discovered that the same effect can be obtained if, instead of the ground state, a very simplified model of the so-called valence-bond solid (VBS) is used, in which the spins are paired in a very ordered way. A spinon in this model can be understood as a single unpaired spin that “travels” through a network of such paired spins.

Importantly, this theoretical prediction was recently successfully confirmed experimentally in the paper by C. Zhao et al. published in Nature Materials.

Spinons and their significance for future technologies

This is an important step towards a better understanding of the quantum properties of magnetics and could open the way to discovering new features of them. Of particular importance, spinons are the result of strong interactions between electrons and quantum phenomena such as quantum entanglement.

Similar mechanisms play a key role in phenomena as fundamental as high-temperature superconductivity or the fractional Hall effect in two-dimensional quantum liquids. Quantum entanglement is also the foundation of quantum computers and quantum computing as a whole.

“Our research not only deepens our knowledge of magnets, but can also have far-reaching consequences in other areas of physics and technology,” concludes Prof Krzysztof Wohlfeld of the Faculty of Physics at the University of Warsaw.

Reference: “Nature of Spinons in 1D Spin Chains” by Teresa Kulka, Miłosz Panfil, Mona Berciu and Krzysztof Wohlfeld, 13 June 2025, Physical Review Letters.
DOI: 10.1103/stvg-lg9h

The research was supported by the National Science Centre under projects 2016/22/E/ST3/00560 (K. W.), 2024/55/B/ST3/03144 (K. W.), 2018/31/B/ST3/03758 (T. K.), 2018/31/D/ST3/03588 (M. P.) and 2022/47/B/ST2/03334. (M. P. ), the University of Warsaw Excellence Initiative (M. P.), the Canada First Research Excellence Fund and the Natural Sciences and Engineering Research Council of Canada (M. B.), and supported in part by NSF grant PHY-2309135 to the Kavli Institute for Theoretical Physics (KITP). The research was conducted with the support of the Interdisciplinary Centre for Mathematical and Computer Modelling at the University of Warsaw (ICM UW) under grant no. G73-29.

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