A new form of matter, in which electrical charge swirls in a vortex, has been observed in a ferroelectric material. The discovery could usher in new kinds of memory and processors that take up far less space.
Scientists from Lawrence Berkeley National Laboratory and the University of California Berkeley have observed these smoothly-rotating polar vortices in carefully manufactured structures made of lead titanate and strontium titanate. The team says they’re similar to similar swirls of magnetism — known as “skyrmions” — that have been seen in the past.
While the swirls of electrical activity have been theoretically hypothesised in the past, this is the first time they’ve been observed experimentally. To see them, the team created carefully repeating layers of lead titanate and strontium titanate, each one just 0.4 nanometres thick. Competing energies within the lattice give rise to some strange effects, as Lane Martin, one of the researchers, explains to PhysOrg:
As we tune the period lengths of our superlattices, we can tune the relative importance of these... energy scales. 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.
Using scanning transmission electron microscopy and X-ray diffraction, the team were able to identify these voticies in the material. You can see them in the image above — the more yellow sections are lead-based, in which the vortices are clearly present. The results are published in Nature.
Like the magnetic vortices can be influenced by magnetic fields, these electrical vortices could be tweaked by external electrical impulses, potentially making them a means of storing data at the nanoscale. Each vortex could, in theory, be coded to hold information. That is some way off, of course — so for now, let’s be content with the scientific discovery. [Nature via PhysOrg]