The group led by Prof. Peng Jiang and Prof. Xinhe Bao from Dalian Institute of Chemical Physics (DICP), Chinese Academy of Sciences (CAS), in collaboration with Associate Prof. Chuanyao Zhou and Prof. Xueming Yang (DICP) as well as Prof. Tun Cao (Dalian University of Technology), made an important progress on the plasmonic properties of Bi₂Te₃ nanoplates. This work has been published in Nano Letters.

Recently, Bi₂Te₂, one of the most studied thermoelectric materials, has drawn great attention due to its fantastic topological properties. Herein, we observe the edge plasmon modes of Bi₂Te₃ in the visible spectral range using femtosecond laser pulse excited photoemission electron microscopy (PEEM, Dreamline BL09U1 of Shanghai Synchrotron Radiation Facility). We propose that the interband transition-induced nonequilibrium carriers might play a key role for the formation of these plasmonic modes. The observation of edge plasmon mode in Bi₂Te₃ not only experimentally demonstrates the possibility of visible plasmons in semiconducting materials beyond traditional noble metals, but also opens up a new avenue toward discovering exotic physical phenomena in quantum topological materials by multi-field modulation.

We acknowledge the valuable help on PEEM measurements from Qunqing Hao, Guanhua Zhang and Julong Sun. This work was supported by National Natural Science Foundation of China (NSFC), National Key Research and Development Program of China and the Youth Innovation Promotion Association of Chinese Academy of Sciences. (Text and figure by Xiaowei Lu)