May 31 2016
Dr. Fan Zhang (Credit: University of Texas at Dallas)
The latest study by UT Dallas physicists may speed up the advancement of more powerful computers and electronics. The researchers are exploring topological insulators, which are materials whose surface electrical properties are opposite to their inside properties.
These materials are made of the same thing throughout, from the interior to the exterior, but, the interior does not conduct electrons — it’s an insulator — while the electrons on the surface are free to move around. The surface is therefore a conductor, like a metal, but it is in fact more robust than a metal.
Dr. Fan Zhang, Assistant Professor of Physics, UT Dallas
The difference between the strong and weak types of topological insulators is small yet significant and involves complicated physics.
“If you had a cube of material that is a strong topological insulator, all six faces can conduct electrons,” said Zhang. “For the weak one, only the four sides are conducting, while the top and bottom surfaces remain insulating.”
At an experimental level, strong topological insulators created soon after they were hypothetically proposed are common in nature said Zhang. So far, many variations have been detected and substantiated experimentally.
However, construction of weak topological insulators is rather vague. Researchers have suggested numerous methods to create a weak topological insulator. Due to its characteristic properties, scientists have been unable to experimentally produce one.
Zhang being a theoretical physicist has suggested a novel method to create a weak topological insulator. The method involves mixing a crystal composed of bismuth with either bromine or iodine. He, along with his co-workers, published their findings recently in the Physical Review Letters journal and delivered a presentation of their study at the March meeting of the American Physical Society.
Zhang said that the German researchers had grown bismuth bromides and iodides in the 1970s; however they failed to identify their potential as weak topological insulators.
This class of materials we are proposing is a unique platform for exploring exotic physics with fairly simple chemistry. With further research and experimentation, our findings could lead to significant advances in technology, especially in electronics and quantum computing.
Dr. Fan Zhang, Assistant Professor of Physics, UT Dallas
The basic building blocks of the conventional transistors that drive electronic devices like computers and cell phones are the electrically conductive materials. Using physics and innovative materials, scientists are recently formulating new experiments and theories in order to develop novel transistor-like technologies that power devices and lead to more powerful computers.
Topological insulators are highly potential as they possess such unique electrical properties, said Zhang.
Our lives have been modified over time by our understanding of the conduction of electrons and the exploitation of this physics for use in electronic devices. We now need to revolutionize transistors. One possible substitution is a so-called topological field effect transistor, which could be made of a thin film of a weak topological insulator.
Dr. Fan Zhang, Assistant Professor of Physics, UT Dallas
Zhang’s research might also support the fundamental redesigning of computers.
“The fundamental computing scale is now very limited,” he said. “For many applications, like weather forecasting and information encoding and decoding, today’s computers are way too slow. However, quantum computers have been proposed that would use the principles of quantum physics to compute exponentially faster than today’s computers.
“Weak topological insulators could make quantum computing feasible.”
Being a theorist, Zhang used old-fashioned paper and pencil to develop his theory about the bismuth compounds.
Dr. Cheng-Cheng Liu, Zhang’s postdoctoral researcher and the project’s lead author, currently Assistant Professor at Beijing Institute of Technology, crunched certain numbers by making use of high-speed supercomputers at the Texas Advanced Computing Center based at UT Austin.
Dr. Bing Lv, Zhang’s UT Dallas co-worker, and Assistant Professor of Physics, has prepared bismuth iodide samples.
The next step will be to characterize the material to explore the unique properties that a weak topological insulator can offer to fundamental physics and to our everyday lives.
Dr. Fan Zhang, Assistant Professor of Physics, UT Dallas
Apart from Zhang and Liu, other authors of the study are Dr. Jin-Jian Zhou from California Institute of Technology and Yugui Yao from Beijing Institute of Technology.
The UT Dallas study was funded by University startup funds and the National Science Foundation through the Aspen Center for Physics and Kavli Institute for Theoretical Physics.