A team led by Rice University physicist Pengcheng Dai has confirmed emergent photon-like behavior in a quantum spin liquid material. The discovery in cerium zirconium oxide verifies a true three-dimensional quantum spin ice. This breakthrough resolves a long-standing puzzle in condensed matter physics.
Physicists have long puzzled over the behavior of quantum spin liquids, materials that defy typical magnetic ordering. In a study published in Nature Physics, researchers verified the existence of emergent photons and fractionalized spin excitations in cerium zirconium oxide (Ce₂Zr₂O₇). Led by Pengcheng Dai, the Sam and Helen Worden Professor of Physics and Astronomy at Rice University, the team used advanced techniques to observe these phenomena at temperatures near absolute zero.
Quantum spin liquids maintain entangled magnetic moments in constant motion, avoiding the orderly patterns seen in conventional magnets. This state mimics aspects of quantum electrodynamics and holds promise for quantum computing and efficient energy transmission. The material Ce₂Zr₂O₇ emerged as a pristine example of a three-dimensional quantum spin ice.
To detect these elusive signals, the researchers employed polarized neutron scattering, which isolated magnetic contributions while minimizing noise as temperatures dropped toward zero. Their data revealed emergent photon signals at low energies, distinguishing quantum spin ice from other magnetic phases. Specific heat measurements further corroborated this, showing dispersion patterns akin to sound waves in solids.
"We've answered a major open question by directly detecting these excitations," Dai said. "This confirms that Ce₂Zr₂O₇ behaves as a true quantum spin ice."
Previous efforts faced challenges from technical limitations and impure samples, but improved preparation and instruments from labs in Europe and North America enabled clearer results. The team also spotted spinons, reinforcing theoretical predictions.
Bin Gao, the study's lead author and a research scientist at Rice, noted the broader impact: "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."
Co-authors include experts from the University of Toronto, Vienna University of Technology, Institut Laue-Langevin, Jülich Centre, and Rutgers University. Funding came from the U.S. Department of Energy, the Gordon and Betty Moore Foundation, and the Robert A. Welch Foundation.
This observation provides a robust platform for exploring entangled quantum matter and its technological applications.