Topological insulators, as new quantum materials, have attracted great attention in condensed matter physics due to their exotic surface property. Recently, theoretical studies have demonstrated that the topological protected surface states are 2D version of Weyl electron. As for 3D, Weyl semimetal possessing “3D surface states” can be achieved in superlattices (SLs) where topological insulators (TIs) are interlaced with normal insulators (NIs). The TI/NI SLs with multiple Dirac channels are predicted to offer great opportunity to design novel materials and investigate new quantum phenomena. More importantly, TI/NI SLs can make the modulation of properties of topological materials become possible.

Prof. Jian Wang at Peking University (PKU), in collaboration with Prof. Xin-Cheng Xie at PKU (theory), Prof. Maohai Xie at HKU (MBE sample growth) and Prof. Yong Wang at ZJU (TEM measurements), firstly and systematically studied the transport property of the artificial TI/NI SL systems. They investigated the quantum transport of SL heterostructure consisted of different thickness of TI layers，and found that tuning the thickness of TI Bi2Se3 layers may completely change the transport dimensionality from 3D to 2D in Bi2Se3/In2Se3 SLs. The discovery demonstrated the feasibility of modulation of topological material property by using TI/NI SLs. This work may stimulate the research on exploring exotic quantum state and potential magneto-conductance, thermoelectric and spintronics applications in TI/NI SLs. The results were published online in Nano Letters (DOI: 10.1021/nl502220p, 2014) with a title of “Crossover from 3D to 2D Quantum Transport in Bi2Se3/In2Se3 Superlattices”. Jian Wang, Xin-Cheng Xie and Mao-Hai Xie are corresponding authors of this paper. Yanfei Zhao and Haiwen Liu contributed equally to this work.

Jian Wang’s group at ICQM, School of Physics, PKU has focused on topological insulators for several years and made a series of achievements in this field with collaborators. Such as electron-electron quantum correction in topological insulators (Physical Review B 83, 245438 (2011)); superconductor-topological insulator interaction (Physical Review B 85, 045415 (2012)); negative magnetoresistance in parallel magnetic field in topological insulator films (Nano Research 5, 739 (2012)); p type and n type topological insulators grown on GaAs substrates (AIP Advances 3, 072112 (2013)); topological insulator heterostructures (Scientific Reports 3, 3060 (2013)); crossover between weak antilocalization and weak localization of bulk states in ultrathin topological insulator films (Scientific Reports 4, 5817 (2014)), and so on.

The work was supported by National Basic Research Programs of China, National Natural Science Foundation of China, 1000 Talents Program for Young Scientists of China, the Research Fund for the Doctoral Program of Higher Education (RFDP) of China, and Collaborative Innovation Center of Quantum Matter, China.