A quantum mystery that stumped scientists for decades is solved
A global research team led by Rice University physicist Pengcheng Dai has verified the presence of emergent photons and
A global research team led by Rice University physicist Pengcheng Dai has verified the presence of emergent photons and fractionalized spin excitations in an unusual quantum spin liquid. Reported in Nature Physics, the work points to the crystal cerium zirconium oxide (Ce2Zr2O7) as a clean three-dimensional example of this exotic state of matter.
Quantum spin liquids have fascinated physicists for years because they could eventually support transformative technologies, including quantum computing and dissipationless energy transmission. Unlike ordinary magnets that settle into an orderly pattern, these materials avoid conventional magnetic order. Instead, their magnetic moments remain strongly quantum-entangled and in constant collective motion at temperatures close to absolute zero, producing behavior that resembles emergent quantum electrodynamics.
“We’ve answered a major open question by directly detecting these excitations,” said Dai, the Sam and Helen Worden Professor of Physics and Astronomy. “This confirms that Ce2Zr2O7 behaves as a true quantum spin ice, a special class of quantum spin liquids in three dimensions.”
Cleaner Measurements With Polarized Neutron Scattering
To pin down these elusive signatures, the researchers relied on advanced polarized neutron scattering. This approach helped them isolate the magnetic scattering they cared about while filtering out other signals, even as the system approached the zero temperature limit.
Their measurements also revealed emergent photon signals near zero energy — a defining trait that separates quantum spin ice from more familiar phases found in conventional magnets. Additional evidence came from specific heat measurements, which supported the idea that these predicted emergent photons follow a dispersion resembling the way sound moves through a solid.
Earlier attempts to confirm this kind of behavior were often undermined by technical noise and incomplete data. The Rice-led team addressed those challenges through improved sample preparation and high-precision instruments, supported by an international effort involving major laboratories across Europe and North America.
First-of-Its-Kind Observation With Big Implications
In this three-dimensional candidate material, the researchers observed both emergent photons and spinons — key hallmarks of quantum spin ice. The result resolves a long-running debate in condensed matter physics and gives scientists a strong platform for studying next-generation quantum phenomena and potential technology pathways.
Bin Gao, a research scientist in Rice’s Department of Physics and Astronomy and the study’s first author, said the findings back up decades of theoretical expectations.
“This surprising result encourages scientists to look deeper into such unique materials, potentially changing how we understand magnets and the behavior of materials in the extreme quantum regime,” Gao said.
Research Team and Funding
Co-authors of this study include Félix Desrochers and Yong Baek Kim of the University of Toronto; Rice alumnus David Tam of the Paul Scherrer Institut; Silke Paschen, Diana Kirschbaum and Duy Ha Nguyen of Vienna University of Technology; Paul Steffens and Arno Hiess of the Institut Laue-Langevin; Yixi Su of Jülich Centre of Heinz Maier-Leibnitz Zentrum; and Sang-Wook Cheong of Rutgers University.
The U.S. Department of Energy, the Gordon and Betty Moore Foundation and the Robert A. Welch Foundation supported this study.
