Magnetic quantum material broadens the platform for testing next-generation information technologies

Scientists at Oak Ridge National Laboratory used neutron scattering to determine whether the atomic structure of a specific material could host a new state of matter called spin-spiral liquid. By tracking tiny magnetic moments known as “spins” in the honeycomb lattice of a layered iron trichloride magnet, the team found the first 2D system that harbors a spiral-spinning liquid.

The discovery provides a testbed for future studies of physical phenomena that may drive next-generation information technologies. These include fractions, or collective quantized vibrations that may hold promise in quantum computing, and skyrmions, or new magnetic spin textures that could advance high-density data storage.

“Materials that host spiral spin liquids are particularly exciting because of their potential to generate quantum spin liquids, spin textures, and fracton excitations,” said ORNL’s Shang Gao, who led the study published in Physical Review Letters.

A long-standing theory predicted that the honeycomb network may harbor a spiral spin liquid, a new phase of matter in which the spins form fluctuating corkscrew-like structures.

However, until the present study, experimental evidence of this phase in a 2D system was lacking. A 2D system comprises a layered crystalline material in which the interactions are stronger in the planar direction than in the stacking direction.

Gao identified iron trichloride as a promising platform to test the theory, which was proposed more than a decade ago. He and co-author Andrew Christianson of ORNL approached Michael McGuire, also of ORNL, who has worked extensively growing and studying 2D materials, and asked if he would synthesize and characterize a sample of iron trichloride for neutron diffraction measurements. Just as 2D graphene layers exist in bulk graphite as honeycomb lattices of pure carbon, 2D iron layers exist in bulk iron trichloride as 2D honeycomb layers. “Previous reports hinted that this interesting honeycomb material might display complex magnetic behavior at low temperatures,” McGuire said.

“Each layer of iron honeycomb has chlorine atoms above and below, forming slabs of chlorine-iron-chlorine,” McGuire said. “The chlorine atoms at the top of one slab interact very weakly with the chlorine atoms at the bottom of the next slab through the van der Waals bond. This weak bond causes materials like this to peel off easily in very thin layers, often down to a single slab. This is useful for developing devices and understanding the evolution of quantum physics from three dimensions to two dimensions.”

In quantum materials, electron spins can behave collectively and exotically. If one spin moves, they all react, a tangled state Einstein called “spooky action at a distance.” The system remains in a state of frustration, a liquid that preserves disorder because electron spins constantly change direction, forcing other entangled electrons to fluctuate in response.

the early neutron diffraction studies of ferric chloride crystals were made at ORNL 60 years ago. Today, ORNL’s extensive experience in material synthesis, imaging, neutron scatteringtheory, simulation, and computation enable pioneering explorations of magnetic quantum materials that drive the development of next-generation technologies for information security and storage

The mapping of spin motions in the spiral spin liquid was made possible by experts and tools at the Spallation Neutron Source and High Flux Isotope Reactor, the DOE Office of Science User Facility at ORNL. . ORNL co-authors were essential to the success of the neutron scattering experiments: Clarina dela Cruz, who led experiments using HFIR’s POWDER diffractometer; Yaohua Liu, who led experiments using SNS’s CORELLI spectrometer; Matthias Frontzek, who led experiments with the HFIR WAND^two diffractometer; Matthew Stone, who led experiments operating SNS’s SEQUOIA spectrometer; and Douglas Abernathy, who led experiments working with SNS’s ARCS spectrometer.

“The neutron scattering data from our SNS and HFIR measurements provided convincing evidence for a spiral-spinning liquid phase,” Gao said.

“The neutron scattering experiments measured how neutrons exchange energy and momentum with the sample, allowing the magnetic properties to be inferred,” said co-author Matthew Stone. He described the magnetic structure of a spiraling liquid: “It looks like a topographical map of a group of mountains with a bunch of rings going outward. If you were to walk the length of a ring, all the turns would point in the same direction. But if you walk out and cross different rings, you’ll see those spins start to rotate around their axes. That’s the spiral.”

“Our study shows that the concept of spiral Spin liquid is viable for the broad class of honeycomb lattice materials,” said co-author Andrew Christianson. “It gives the community a new route to explore spin textures and novel excitations, such as fractions, that can then be used in future applications such as quantum computing.”

The title of the article is “Spiral liquid spiraling in a honeycomb lattice”.