By cooling an atom-thin magnetic material, physicists have experimentally confirmed a classic 1970s model of two-dimensional magnetism.
Bizarre things happen when materials are thinned from bulk crystals down to layers just one atom thick. In a study published in Nature Materials, physicists at The University of Texas at Austin reported that they have observed a series of unusual magnetic states in an ultrathin material.
Their experiments provide the first complete demonstration of a theoretical model of two-dimensional magnetism that was introduced in the 1970s. According to the team, the findings could help guide the development of future ultracompact technologies.
The newly observed behavior involves two major magnetic transitions that occur as certain materials are cooled toward absolute zero. Although scientists have previously detected each transition separately, this is the first time both have been seen together as part of the full predicted sequence.
To carry out the experiment, the researchers cooled a single layer of nickel phosphorus trisulfide (NiPS3) to temperatures between –150 and –130 °C. Within this range, the material entered an unusual magnetic state known as a Berezinskii–Kosterlitz–Thouless (BKT) phase. In this phase, the tiny magnetic directions associated with individual atoms, known as magnetic moments, organize into swirling configurations called vortices. These vortices form in pairs that rotate in opposite directions, one clockwise and the other counterclockwise, and the paired structures remain closely linked rather than separating.
The Berezinskii–Kosterlitz–Thouless Phase
The BKT phase is named for physicist Vadim Berezinskii and for J. Michael Kosterlitz and David Thouless, who received the 2016 Nobel Prize in Physics for developing the theory that describes this type of transition.
“The BKT phase is particularly intriguing because these vortices are predicted to be exceptionally robust and confined to just a few nanometers laterally while occupying only a single atomic layer in thickness,” said Edoardo Baldini, assistant professor of physics at UT and leader of the research. “Because of their stability and extremely small size, these vortices offer a new route to controlling magnetism at the nanoscale and provide insight into universal topological physics in two-dimensional systems.”
Completing the Six-State Clock Model
When the material was cooled even further, it shifted into a different magnetic arrangement known as a six-state clock ordered phase. In this configuration, the magnetic moments settle into one of six symmetry-related directions. Observing both the BKT phase and this lower temperature ordered phase confirms the full set of transitions predicted by the two-dimensional six-state clock model, an influential theoretical framework proposed in the 1970s.
“At this stage, our work demonstrates the full sequence of phases expected for the two-dimensional six-state clock model and establishes the conditions under which nanoscale magnetic vortices naturally emerge in a purely two-dimensional magnet,” Baldini said.
Toward Higher-Temperature Applications
The team’s next goal is to determine how to adjust material properties so that similar magnetic phases can remain stable at progressively higher temperatures, potentially reaching room temperature. Achieving that would make these effects far more practical for real world applications. This first experimental confirmation lays the groundwork for that effort.
The results also suggest that nickel phosphorus trisulfide is not unique. Other two-dimensional magnetic materials may host related and as yet undiscovered phases. That possibility opens new opportunities for both fundamental research and the design of future nanoscale devices built around precisely controlled magnetism.
Reference: “Six-state clock physics in an atomically thin antiferromagnet” by Frank Y. Gao, Dong Seob Kim, Chao Lei, Ajesh Kumar, Xinyue Peng, Xiaohui Liu, Francesco Barantani, Shangjie Zhang, Kyoung Pyo Lee, Kalaivanan Raju, David Lujan, Saba Arash, Sankar Raman, Shang-Fan Lee, Mengxing Ye, Xiaoqin Li, Allan H. MacDonald and Edoardo Baldini, 23 February 2026, Nature Materials.
DOI: 10.1038/s41563-026-02516-7
This research was primarily supported by the National Science Foundation (NSF) through UT’s Center for Dynamics and Control of Materials, an NSF Materials Research Science and Engineering Center. Work in the Baldini group was additionally supported by Love, Tito’s; the Robert A. Welch Foundation; the W. M. Keck Foundation; the NSF through a CAREER award; the U.S. Air Force Office of Scientific Research through a Young Investigator Program award; and the U.S. Army Research Office.
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2 Comments
In the alternate theory proposed by me, electromagnetic energy of unit charge is finite and is conserved. In any material, part of that energy manifests as magnetic energy, and the rest electrostatic energy remains completely used. Any unused magnetic energy creates a net magnetic field.
It is the balance between attractive and repulsive forces (motion also acts as repulsive force) that provides stability to the material. So in a one atoms thick material this can create very interesting patterns.
Other two-dimensional magnetic materials may host related and as yet undiscovered phases. That possibility opens new opportunities for both fundamental research and the design of future nanoscale devices built around precisely controlled magnetism.
VERY GOOD.
Please ask researchers to think deeply:
Are you observing two-dimensional materials?
If we cease asking “whether observation disturbs the object” and instead ask “how observation participates in the topological variation of the object,” our understanding of scientific knowledge may enter a new realm.
—— Excerpted from https://zhuanlan.zhihu.com/p/2010973729556026200.
What makes skyscrapers, bridges, and tunnels different from one another is not the steel reinforcement, cement, and sand they are composed of, but the difference in their spatial structure.
—— Excerpted from https://zhuanlan.zhihu.com/p/2012896837590360214.