Researchers were recently surprised to discover that what was thought to be a quantum state is actually an entirely new phase of matter, the potential applications for which are still being determined in a significant physics development.
Researchers’ interest in exotic states of matter and quantum computers has long focused on magnetic materials in the quantum spin-liquid phase. In a recent paper published in Science Advances, researchers demonstrated that, despite evidence suggesting that magnesium hexalluminate (CeMgAl11O19) was in a quantum spin liquid phase, it was actually inhabiting an entirely new phase of matter.
Typical States of Matter
“The material had been classified as a quantum spin liquid due to two properties: observation of a continuum of states and lack of magnetic ordering,” said Bin Gao, co-first author and a research scientist at Rice. “But closer observation of the material showed that the underlying cause of these observations wasn’t a quantum spin liquid phase.”
CeMgAl11O19 is an insulating material in which its magnetic ions can adopt either a ferromagnetic or antiferromagnetic state. Typically, when one ion enters a ferromagnetic state, it triggers a domino effect that pulls surrounding ions into the same alignment. The opposite can also occur, as ions shift into antiferromagnetic states.
Cooling the material to extremely low temperatures, near absolute zero, allows scientists to observe the magnetic alignment clearly. At such frigid temperatures, ions in non-quantum materials settle into a low-energy configuration. As a result, when researchers observe the material, they typically see only a single configuration—either ferromagnetic or antiferromagnetic.
Quantum States of Matter
This behavior changes in quantum spin-liquid materials, where quantum mechanics causes the system to transition between low-energy states in markedly different ways, producing a continuum of states. Additionally, the quantum state lacks magnetic ordering, allowing both ferromagnetic and antiferromagnetic interactions to coexist.
When observing CeMgAl11O19, the team detected a continuum of magnetic states and a lack of magnetic ordering—features typically associated with quantum states. However, closer analysis revealed that competition between ferromagnetic and antiferromagnetic interactions, rather than promoting the material existing in a quantum state, was doing just the opposite.
“This was very unexpected for us,” co-author Pengcheng Dai told The Debrief. “To discover a new nonquantum state of matter that behaves like a quantum spin liquid is exciting because such a state can be quantitatively calculated using known theory. We can have [an] exact comparison between theory and experimental results.”
“We were interested in this material, which had a collection of characteristics we hadn’t seen before,” said Tong Chen, co-first author and a research scientist at Rice. “It was not a quantum spin liquid, yet we were observing what we thought were quantum spin liquid-associated behaviors.”
Continuing to Investigate
The team examined the material using several experimental techniques and bombarded it with neutrons, allowing them to gather evidence that CeMgAl11O19 features an unusually weak boundary between ferromagnetic and antiferromagnetic states. Because the ions are relatively free to shift between these states, stable magnetic ordering does not occur in the material.
As a result, when the team cooled the material to nearly absolute zero, many observable states appeared in a manner typical of a quantum spin liquid—yet the system could not transition between them in the way a true quantum state would.
“The material’s unique ability to ‘choose’ between different low energy states produced observational data very similar to a quantum spin liquid state,” Dai said. “This is a new state of matter that, to our knowledge, we are the first to describe.”
“[Practical applications are] not clear yet at this point,” Dai said. “But revealing a new state of matter is always an important and exciting development. In science, many times when we initially discovered a new phenomenon, we don’t really know how that can be used at the time of discovery.”
The researchers are continuing to investigate the discovery, with current work focused on intentionally manipulating the new phase of matter.
The paper, “Spin Excitation Continuum from Degenerate States in the Mixed Ferro-Antiferromagnetic Exchange System CeMgAl11O19,” appeared in Science Advances on March 6, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.