Magnetic quantum material expands the platform for researching next-generation information technologies

Magnetic quantum material expands the platform for researching next-generation information technologies

Neutron scattering showed spin correlations of iron trichloride. An artist’s rendering interprets the scattering providing evidence for a spiral spin liquid state. Credit: Jacquelyn DeMink/ORNL

Scientists at Oak Ridge National Laboratory used neutron scattering to determine whether a given material’s atomic structure could harbor a novel state of matter called spiral spin liquid. By tracking tiny magnetic moments known as “spins” on the honeycomb lattice of a layered iron trichloride magnet, the team found the first 2D system harboring a helical spin liquid.

The discovery provides a testbed for future studies of physical phenomena that could advance next-generation information technologies. These include fractons, or collective quantized oscillations, which could show promise for quantum computing, and skyrmions, or novel magnetic spin textures, which could drive high-density data storage.

“Materials containing spiral spin liquids are particularly exciting because they can be used to generate quantum spin liquids, spin textures and fractional excitations,” said ORNL’s Shang Gao, who led the study published in Physical Verification Letters.

A long-held theory predicted that the honeycomb lattice could host a helical spin fluid – a novel phase of matter in which spins form fluctuating corkscrew-like structures.

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

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

“Each honeycomb layer of iron has chlorine atoms above and below it, creating chlorine-iron-chlorine plates,” McGuire said. “The chlorine atoms on one plate interact very weakly with the chlorine atoms on the bottom of the next plate through van der Waals bonding. This weak bond makes materials like this easily apart into very thin layers, often down to a single sheet. This is useful for designing devices and understanding the evolution of quantum physics from three dimensions to two dimensions.”

In quantum materials, electron spins can behave collectively and exotically. When one spin moves, everyone reacts—an entangled state that Einstein called “spooky action at a distance.” The system remains in a state of frustration—a fluid that preserves disorder because electron spins are constantly changing direction, forcing other entangled electrons to fluctuate in response.

The first neutron diffraction studies on ferric chloride crystals were performed at ORNL 60 years ago. Today, ORNL’s extensive expertise in materials synthesis, imaging, neutron scattering, theory, simulation and computation enables pioneering research into quantum magnetic materials, driving the development of next-generation technologies for information security and storage.

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, user facilities of the DOE Office of Science at ORNL. ORNL co-authors were essential to the success of the neutron scattering experiments: Clarina dela Cruz, who led experiments with HFIR’s POWDER diffractometer; Yaohua Liu, who led experiments with SNS’s CORELLI spectrometer; Matthias Frontzek, who led experiments with HFIR’s WAND2 diffractometer; Matthew Stone, who led experiments with SNS’ SEQUOIA spectrometer; and Douglas Abernathy, who led experiments with SNS’s ARCS spectrometer.

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

“The neutron scattering experiments measured how the neutrons exchange energy and momentum with the sample, allowing inferences about the magnetic properties,” said co-author Matthew Stone. He described the magnetic structure of a spiral spin liquid: “It looks like a topographical map of a mountain range with a bunch of rings going outwards. If you walked along a ring, all of the spins would point in the same direction. But if you go outside and cross different rings, you’ll see how these spins start rotating around their axes.

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

The title of the work is “Spiral Spin Liquid on a Honeycomb Lattice”.

Researcher uses HFIR to explore the mysterious world of quantum spins

More information:
Shang Gao et al., Spiral Spin Liquid on a Honeycomb Lattice, Physical Verification Letters (2022). DOI: 10.1103/PhysRevLett.128.227201

Provided by Oak Ridge National Laboratory

Quote: Magnetic Quantum Material Broadens Platform for Sonding Next-Gen Information Technologies (2022, July 27), retrieved July 27, 2022 from platform.html

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