Scientists at Oak Ridge National Laboratory used neutron scattering to determine whether the atomic structure of a particular substance could host a new state of matter called spin-helical fluid. By tracing the tiny magnetic moments known as “spins” on the honeycomb lattice of a ferric trichloride magnet, the team found the first two-dimensional system hosting a spinning spiral fluid.
This discovery provides a testing base for future studies of physics phenomena that may drive next-generation information technologies. These include fractions, or collective quantum vibrations that may prove promising in quantum computing, the sky, or new magnetic materials that could enhance high-density data storage.
ORNL’s Shang Gao, who led the study published in, said: physical review messages.
A long-standing theory has predicted that the honeycomb lattice could host a helical fluid — a new phase of matter in which the spindles form fluctuating helix-like structures.
However, until this study, experimental evidence for this stage in a two-dimensional system was lacking. The two-dimensional system includes a layered crystalline material in which the interactions are stronger in the plane 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 contacted Michael McGuire, also of ORNL, who has worked extensively on the cultivation and study of 2D materials, asking if he would synthesize and characterize a sample of iron trichloride for neutron diffraction measurements. Like 2D graphene layers present in bulk graphite as pure carbon honeycomb networks, 2D iron layers in bulk iron trichloride as 2D honeycomb layers. “Previous reports have indicated that the intriguing honeycomb material can exhibit complex magnetic behavior at low temperatures,” McGuire said.
Each layer of iron is shaped like a beehive chlorine atoms above and below it, making chlorine, iron, and chlorine panels,” McGuire said. The chlorine atoms at the top of one plate interact very weakly with the chlorine atoms at the bottom of the next plate through the van der Waals bond. This poor bonding makes materials like this easy to peel into very thin layers, often all onto a single sheet. 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 both collectively and strangely. If you move one cycle, they all interact – an entangled state that Einstein called “spooky action at a distance.” The system remains in a state of frustration—a fluid that maintains chaos because the electron is constantly changing direction, forcing the other entangled electrons to oscillate in response to the response.
The First neutron diffraction studies of ferric chloride crystals were conducted at ORNL 60 years ago. Today, ORNL’s extensive experience in material synthesis, imaging, neutron scatteringtheory, simulation and computation enable groundbreaking explorations of magnetic quantum materials that drive the development of next-generation technologies for Information Security and storage.
Mapping of spin motions in a helical spin fluid is made possible by experts and tools at the Spallation Neutron Source and High Flow Isotope Reactor, and DOE Office of Science user facilities at ORNL. ORNL co-authors were essential to the success of the neutron scattering experiments: Clarina Della Cruz, who led the experiments with a HFIR powder diffractometer; Yaohua Liu, who led the experiments using SNS’s CORELLI spectrometer; Matthias Frunzik, who led the experiments using HFIR’s WAND2 diffractometer. Matthew Stone, who led experiments to operate SNS’s SEQUOIA spectrometer; and Douglas Abernathy, who led SNS’s ARCS spectrometer work trials.
“The neutron scattering data from our measurements in the SNS and HFIR provided convincing evidence for the existence of a chiral liquid phase,” Gao said.
Neutron scattering experiments measured how the neutrons exchange energy and momentum with the sample, allowing the magnetic properties “It can be inferred,” co-author Matthew Stone said, describing the magnetic structure of a helical spiral fluid: “It looks like a topographic map of a group of mountains with a bunch of rings pointing outward. If you were to walk along a loop, all the cycles would point in the same direction. But if you walked out and through different loops, you’ll see that those cycles around their axes. That’s the helix.”
The title of the paper is “Spiral Spin Liquid on a Honeycomb Lattice”.
Shang Gao et al, Spiral Spin Liquid on Honeycomb Grid, physical review messages (2022). DOI: 10.1103/ PhysRevLett.128.227201
Oak Ridge National Laboratory
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