Experimental observation of the quantization in surface Dirac states of topological insulator -Towards the application of low-power electric devices-



R. Yoshimi, A. Tsukazaki, Y. Kozuka, J. Falson, J. G. Checkelsky, K. S. Takahashi, N. Nagaosa, M. Kawasaki and Y. Tokura



Topological insulators are an unusual class of materials, which do not conduct electricity in the inside but only on the surfaces. Their surfaces are the Dirac states populated by massless electrons and holes—known as Dirac fermions. As a result, their properties are being studied intenvively with the hope of creating low-power consumption electronic devices. However, small amount of inside conduction due to impurities and defects in the crystal have, up to now, made it difficult to realize the pure conduction of surface Dirac states.

In the current research, the group established the growth of high quality thin film of (Bi0.12Sb0.88)2Te3, one of topological insulators, with eliminating the impurities and defects to realize the insulating state inside the film. They transformed the films into electric gating devices known as "field effect transistors," and measured the Hall resistance, while changing the number of electrons in the sample.. By doing this, they were able to show that the resistance became constant (at approximately 25.8 kOhms), demonstrating the presence of the quantum Hall effect in the material. These results are expected to promote the application of fast and low-power consumption electronics.