Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Polar vortices observed in ferroelectric

01.02.2016

New state of matter holds promise for ultracompact data storage and processing

The observation in a ferroelectric material of "polar vortices" that appear to be the electrical cousins of magnetic skyrmions holds intriguing possibilities for advanced electronic devices. These polar vortices, which were theoretically predicted more than a decade ago, could also "rewrite our basic understanding of ferroelectrics" according to the researchers who observed them.


The first ever observations of polar vortices in a ferroelectic material could find potential applications in ultracompact data storage and processing and the production of new states of matter.

Credit: Berkeley Lab

A team of scientists with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have recorded the first ever observations of rotating topologies of electrical polarization that are similar to the discrete swirls of magnetism known as "skyrmions." If these smoothly rotating vortex/anti-vortex topologies prove to be electrical skyrmions, they could find potential applications in ultracompact data storage and processing, and could also lead to the production of new states of matter and associated phenomena in ferroic materials.

"It has long been thought that rotating topological structures are confined to magnetic systems and aren't possible in ferroelectric materials, but through the creation of artificial superlattices, we have controlled the various energies of a ferrolectric material to promote competition that lead to such new states of matter and polarization arrangements," says Ramamoorthy Ramesh, Berkeley Lab's Associate Laboratory Director for Energy Technologies and the co-principal investigator for this study. He also holds UC Berkeley's Purnendu Chatterjee Endowed Chair in Energy Technologies.

"Ferroelectric materials such as the materials used in this work

have produced a number of exciting emergent properties over the years, but these smoothly-rotating polar vortex structures really are different," says Lane Martin, a faculty scientist with Berkeley Lab's Materials Sciences Division and Associate Professor in UC Berkeley's Department of Materials Science and Engineering, who is this study's co-principal investigator. "I think if you surveyed the community many would shake their heads in disbelief at such structures, but it turns out there really is a tendency for vortex states to form in nature even in these polar systems. And, when one looks more broadly, vortex structures can occur across huge length scales - from galaxies and weather systems all the way down to 10s of atoms as in our case."

Ramesh and Martin are the corresponding authors of a Nature paper describing this study in detail. The paper is titled "Observation of Polar Vortices in Oxide Superlattices." The lead researchers on this work are Ajay Yadav, Christopher Nelson, and Anoop Damodaran who also hold joint appointments with Berkeley Lab and UC Berkeley. (Full list of authors below.)

Ferroic materials display unique electrical or magnetic properties - or both in the case of multiferroics. For example, the electrical field of a ferroelectric material can be polarized in favor of either a positive or negative charge with the application of an external electrical field. In a ferromagnetic material, the application of an external magnetic field aligns the spin of their charged particles, resulting in the material becoming a permanent magnet. In recent years, it was discovered that the application of an external magnetic field can also produce atom-sized cyclones of skyrmions, which act like baryon particles and can be moved coherently over macroscopic distances. These properties make skyrmions excellent candidates for spintronic applications.

"We believe the polar vortices we observed in ferroelectrics, when fully explored, have the potential to be topological states of matter that are similar to magnetic skyrmions," Ramesh says. "The fact that our polar vortices can display emergent behavior in their electronic, optical, magnetic and other properties suggests that heretofore unexplored applications and functionalities could be possible."

Ramesh, Martin and their collaborators worked with what has become a canonical system in the community, ultrafine layered structures built from lead titanate and strontium titante compounds controlled down to a few unit cells each, in which each unit cell is approximately 0.4 nanometers thick. They created superlattices that harbored a three-way competition between elastic, electrostatic and gradient energies within the layers of lead titanate and strontium titanate. This unique three-way competition gives rise to the polar vortices.

"As we tune the period lengths of our superlattices, we can tune the relative importance of these three energy scales," Martin says. "Although rather exotic things can occur if one changes the superlattice period to be both smaller and bigger than we studied here, we really found the 'sweet-spot' in this work that produced these polar vortices which are an entirely new phenomenon."

A combination of scanning transmission electron microscopy (STEM) and X-ray diffraction studies were used observe and characterize the polar vortices. The STEM work was carried out at Berkeley Lab's Molecular Foundry, a DOE Office of Science User Facility, on TEAM 0.5, the world's most powerful transmission electron microscope. The X-ray diffraction work was carried out at the Advanced Photon Source, another DOE Office of Science User Facility, which is hosted by DOE's Argonne National Laboratory.

"Our study is really indicative of how DOE-funded research programs can bring together a diverse range of expertise, including atomically-controlled materials synthesis and cutting-edge research facilities, and materials theory to enable foundational discoveries that really change the way we think about exotic materials and the possibilities for using them," says Ramesh.

"This is just the beginning for the study of polar vortices in ferroelectric materials," Martin says. "We're observing a new state of matter and we have our work cut out for us in mapping and understanding how it evolves. We can imagine adding a magnetic spin component to similar superlattices and thus potentially paving a pathway to fundamentally demonstrate electric-field control of magnetism."

###

Other co-authors of the Nature paper were Shang-Lin Hsu, Zijian Hong, James Clarkson, Christian Schlepüetz, Anoop Damodaran, Padraic Shafer, Elke Arenholz, Liv Dedon, Deyang Chen, Ashvin Vishwanath, Andrew Minor, Long-Qing Chen and Jason Scott.

This research was primarily funded by the DOE Office of Science.

Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www.lbl.gov.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/.

Lynn Yarris | EurekAlert!

More articles from Physics and Astronomy:

nachricht Pulses of electrons manipulate nanomagnets and store information
21.07.2017 | American Institute of Physics

nachricht Vortex photons from electrons in circular motion
21.07.2017 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA looks to solar eclipse to help understand Earth's energy system

21.07.2017 | Earth Sciences

Stanford researchers develop a new type of soft, growing robot

21.07.2017 | Power and Electrical Engineering

Vortex photons from electrons in circular motion

21.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>