Press Releases
Oct. 12, 2011

A new two-dimensional topological insulator

— Successful formation of a bilayer bismuth —
  • Toru Hirahara (Department of Physics, University of Tokyo)
  • Shuji Hasegawa (Department of Physics, University of Tokyo)
  • Shin-ichi Kimura (UVSOR facility, Institute for Molecular Science)


Figure 1

Figure: The experimental band dispersion of Bi(111) bilayer on Bi2Te3 measured experimentally (left) and its corresponding first-principles calculations (right). The left bottom figure shows the schematic drawing of a two-dimensional topological insulator.

Topological insulators are a new state of matter which is gaining increased attention in condensed matter physics. While the bulk is an insulator, they have metallic edge (surface) states and these edge states have similar properties with magnets even though the bulk is not a magnet. There are hopes to develop novel devices utilizing this intriguing property.

In the present work, the research group led by assistant professor Dr. Toru Hirahara at the department of physics has found a way to fabricate a new two-dimensional topological insulator. The remarkable thing about this material is that it is only two-atomic layers (bilayer) thick made of bismuth. While it is not impossible to make such a thin material in the atomic scale (for example, the Noble physics prize in 2010 was awarded to physicists who studied graphene, a single atomic-layer sheet of carbon), it still remains to be a big challenge. The present finding should accelerate researches to further understand the exotic properties of topological insulators as well as those for application in atomic-scale devices and quantum computation.

Paper information

Toru Hirahara1, Gustav Bihlmayer2, Yusuke Sakamoto1, Manabu Yamada1, Hidetoshi Miyazaki3, Shin-ichi Kimura3, Stefan Blügel2, Shuji Hasegawa1
(1 Department of physics, University of Tokyo, 2 Forschungzentrum Jülich, 3 UVSOR facility, Institute for Molecular Science)

Interfacing 2D and 3D Topological Insulators: Bi(111) Bilayer on Bi2Te3
Physical Review Letters (PRL)