Different structure evolution in Bi2Se3 - Lin Wang

NOVEMBER 2, 2015

Dr. Lin Wang and Zhenhai Yu from HPSTAR, led an international group of collaborators, found two pressure-induced structural phase transitions in topological insulator, Bi₂Se₃ in their recent study, which follows differently in the structure transformation compared with its isostructural compounds, Bi2Te3 and Sb2Te3.

The crisis of energy prompts researchers to explore green/sustainable energy. Thermoelectric materials (such as Bi₂Te₃and Bi₂Se₃), as the typical sustainable energy materials used in thermoelectric systems for cooling or heating could also be applied to regenerate electricity from waste heat at electric power plants. While topological insulators (TIs) are electronic materials that have a bulk band gap like ordinary insulators, but feature conducting states on their surface, which  are one of the most exciting topics in condensed-matter physics, with a wide range of potential practical applications. Topological insulators (TIs) found in the thermoelectric materials such as Bi₂Te₃, Sb₂Te₃, and Bi₂Se₃ hit the physics spotlight as another exciting newcomer, which act like insulators on the interior, while conduct on the surface.

For isostructural materials, it’s nature to assume a similar/same structure transition pathway under the same conditions.  Still, different crystal structure or electronic structure transitions are detected in some isostructural materials. The team led by Dr. Wang, utilized diamond-anvil cell technology, x-ray diffraction, Raman spectroscopy combined with theoretical simulations to track the structure evalution in Bi₂Se₃, one of the important TIs. At ambient conditions,  Bi₂Se₃ isostructural to Bi₂Te₃ and Sb₂Te_3. The researchers found that the TI in question, Bi₂Se₃ displays a progressive structural evolution compared with Bi₂Te₃ and Sb₂Te_3. It transferred from an ambient rhombohedra structure to a monoclinic phase and eventually to a body-centered tetragonal phase instead of the recently reported disordered body-centered cubic (BCC) phase. “This remarkable difference in atomic radii of Bi and Se in Bi₂Se₃ may explain why Bi₂Se₃ shows different structural behavior from the isocompounds Bi₂Te₃ and Sb₂Te₃” , said Dr. Zhenghai Yu, whose research mainly focus on gaining better understanding of the nature of phase transition in functional materials.

The work is published in Sci. Rep. 5, 15939; doi: 10.1038/srep15939 (2015).

Caption: Structural evolution in Bi₂Se₃ under high pressure.