Topological insulators are materials that are electrical insulators in the bulk but can conduct electricity on their surface via special surface electronic states. The ability to conduct on the surface happens because electrons reside on the surface are ordered differently from ordinary materials. This ordering happens as the result of a physical concept called ‘topology’. This leads to some special properties.
A new review of topological insulators has been provided by physicists from the University of Groningen. The review looks at current development problems as well as with future applications.
The electrons ordered on topological insulators have the values ‘up’ or ‘down’ locked into their movement, according to Controlled Environments magazine. In practice this means electrons moving to the right have spin down and those moving to the left have spin up. However, when electrons are injected into the insulator they always travel to the left. This special property sparks an interest in the field of spintronics. This is about developing electronics based on the quantized spin value rather than the charge of electrons. Spintronics fundamentally differs from traditional electronics in that, in addition to charge state, electron spins are exploited as a further degree of freedom, with implications in the efficiency of data storage and transfer.
Why do spintronics matter?
Technologists and physicists are interested in spintronics because spintronic systems are of particular interest in the field of quantum computing. Quantum computing promises greatly enhanced computing power. Since less energy is needed to change spin than to generate a current to maintain electron charges in a device, spintronics devices would use less power. For computers this would significantly increase the rate at which information could be read from a hard disk drive. For this reason materials that facilitate spintronics are of great interest to technology companies.
What has limited development is that practical experiments have yielded mixed results, according to Dr. Tamalika Banerjee and Eric de Vries, who have led the material review. The mixed results are due to stray magnetic fields. Pinpointing this also allows ways to overcome this effect, and new approach to be taken with topological insulators. The new approach uses the application of stronger magnetic fields. One study used a 33-Tesla magnet, which is one of the strongest magnets in the world. Improvements are also boosted through the way crystals are prepared.
Here initial trials have been successful and the results signal new ways to improve topological insulators.
The review has been published in the journal Physical Review B. The research is titled “Coexistence of bulk and surface states probed by Shubnikov–de Haas oscillations in Bi2Se3 with high charge-carrier density.”
