Bulkier is Better?

Photo courtesy of Roy Kaltschmidt

Beamline 4.0.2 at Berkeley Lab's Advanced Light Source.

While slimming down is a popular goal, particularly at this time of year, bulking up can be even better in some cases. That could be true for a new material recently discovered by researchers at two Office of Science laboratories, which could have some well, wide applications.

Specifically, a team that included researchers at two Office of Science Labs, Lawrence Berkeley National Laboratory (Berkeley Lab) and SLAC National Accelerator Laboratory (SLAC), recently found a 3D counterpart to one of the flattest of them all, the amazing material graphene.

Graphene is effectively a 2D material, consisting of single layers of carbon atoms connected in honeycomb-like structures. It's also a material with extraordinary properties. Graphene crystals are harder than diamond and stronger than steel, yet the material is stretchable and almost transparent while conducting electricity better than copper. It's also potentially a superconductor: Charge-carrying electrons race through specially treated or "doped" graphene far faster than they do in silicon, which gives it great potential for use in high-performance electronic devices, such as exceptionally fast sensors and transistors.

However, graphene is tough and costly to make in large quantities, and its 2D structure makes for other limitations. As a consequence, scientists have been striving to find 3D materials with similar properties. And thanks to a team that included researchers at Berkeley Lab and SLAC, they may have found one in sodium bismuthate. Yulin Chen, a physicist at Oxford, led the study and used Berkeley Lab's Advanced Light Source to confirm the properties of the material. His counterpart at SLAC was Zhongkai Liu, and scientists at both labs contributed to the discovery.

Sodium bismuthate isn't a perfect counterpoint to graphene, but it does share its affinity for ultrafast electrons. Both materials are also topological insulators, meaning that they are electrical conductors on the surface, but insulators within.

Enlarge Photo

Photo courtesy of Brad Plummer/SLAC

Zhongkai Liu is a graduate student with the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC and one of two lead authors on the research.

Topological insulators are especially interesting to researchers since they lock in the spins of the electrons flowing within. In conventional electronic devices, information is simply carried by the charge of the electron. However, electrons also spin – either up or down – and if scientists could tap that spin, it could open the way to their carrying much more information, and thus the creation of faster and more electronic versatile devices. That's the developing field of spintronics, and the discovery of sodium bismuthate could lead to new advances in the area.

For all its signal similarities to graphene, sodium bismuthate won't replace its conducting carbonous counterpart anytime soon. That's due to its unfortunate habit of bubbling and then turning into powder when exposed to air. However, its discovery opens the door to the detection or creation of other materials that are more stable than sodium bismuthate and easier to make than graphene.

The work might also show scientists better ways to combine superconductivity with spintronics and eventually point to new materials through which information-laden electrons simply fly – the aerial equivalent of a cargo jet that screams at hypersonic speeds – which could show up in the form of much faster transistors and far more compact hard drives.

From thin and fast to bulkier and even faster: That's the potential of discovery in action, and that's the Office of Science at work.

The Department'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 http://science.energy.gov/about. For more information about Berkeley Lab please go to: http://www.lbl.gov/.

Charles Rousseaux is a Senior Writer in the Office of Science, Charles.rousseaux@science.doe.gov.