"Electronic structure of monolayer 1T′-MoTe2 grown by molecular beam epitaxy"

Shujie Tang: Chaofan Zhang, Chunjing Jia, Hyejin Ryu, Choongyu Hwang, Makoto Hashimoto, Donghui Lu, Zhi Liu, Thomas P. Devereaux, Zhi-Xun Shen and Sung-Kwan Mo; APL Materials, 11/14/17.

Additional Authors: Chaofan Zhang, Chunjing Jia, Hyejin Ryu, Choongyu Hwang, Makoto Hashimoto, Donghui Lu, Zhi Liu, Thomas P. Devereaux, Zhi-Xun Shen and Sung-Kwan Mo

Abstract:

Monolayer transition metal dichalcogenides (TMDCs) in the 1T′ structural phase have drawn a great deal of attention due to the prediction of quantum spin Hall insulator states. The band inversion and the concomitant changes in the band topology induced by the structural distortion from 1T to 1T′ phases are well established. However, the bandgap opening due to the strong spin-orbit coupling (SOC) is only verified for 1T′-WTe2 recently and still debated for other TMDCs. Here we report a successful growth of high-quality monolayer 1T′-MoTe2 on a bilayer graphene substrate through molecular beam epitaxy. Using in situangle-resolved photoemission spectroscopy (ARPES), we have investigated the low-energy electronic structure and Fermi surface topology. The SOC-induced breaking of the band degeneracy points between the valence and conduction bands is clearly observed by ARPES. However, the strength of SOC is found to be insufficient to open a bandgap, which makes monolayer 1T′-MoTe2 on bilayer graphene a semimetal.