New method of controlling the properties of topological insulators could lead to the development of superfast quantum computers and more energy-efficient transistors, memory devices and magnetic sensors.
Physicists at the University of Michigan have developed a more controlled method to fine-tune the properties of topological insulators—materials with the unique ability to conduct electricity on their surface while acting simultaneously as an insulator to block the flow of current internally. Scientists believe topological insulators, discovered less than a decade ago, could enable the development of superfast quantum computers and more energy-efficient transistors, memory devices and magnetic sensors.
The new, more controlled method of creating topological insulators utilizes a technique known as doping, in which small amounts of impurities are added to a material in order to change its electrical conductivity. In this case, University of Michigan researchers added thallium, a poisonous metal, to bismuth telluride, a mirror-like substance known for its ability to convert heat to electricity. The paper has been published online in Physical Review B.
With the new method, the researchers can alter the properties of the material from a “p-type” semiconductor, which conducts electricity because of a deficiency of electrons, to an “n-type” semiconductor, which conducts electricity because of an excess of electrons, while “locking” the material in the middle.
“This is a more elegant approach to making a topological insulator,” Ctirad Uher, the C. Wilbur Peters Collegiate Professor of Physics in the College of Literature, Science and the Arts, said. “By doping with thallium, we can add electrons to the system and take it across the full spectrum of carrier densities.” The “carriers” Uher is referring to are electrons and holes, areas that act as positively charged particles to keep electrons moving in a current.
“Topological insulators are one of the most exciting fields right now in condensed matter physics,” Hang Chi, a doctoral student in physics at the university, said. “Because they have a bulk that is insulating, and a surface that is conducting, they can be used for quite a lot of applications—perhaps quantum computation, for example. They could also house so-called Majorana fermions [matter particles that are their own antiparticle].”