Published in Nano Lett. (2015), DOI: 10.1021/acs.nanolett.5b01968.
Probing critical point energies of transition metal dichalcogenides: surprising indirect gap of single layer WSe2
Chendong Zhang1, Yuxuan Chen1, Amber Johnson1, Ming-Yang Li2, Lain-Jong Li3, Patrick C. Mende4, Randall M. Feenstra4 and Chih-Kang Shih1
1Department of Physics, University of Texas at Austin, Austin, TX 78712, USA
2Institute of Atomic and Molecular Sciences, Academia Sinica, No. 1, Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan
3Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia
4Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
Abstract
By using a comprehensive form of scanning tunneling spectroscopy, we have revealed detailed quasi-particle electronic structures in transition metal dichalcogenides, including the quasi-particle gaps, critical point energy locations and their origins in the Brillouin zones. We show that single layer WSe2 surprisingly has an indirect quasi-particle gap with the conduction band minimum located at the Q point (instead of K), albeit the two states are nearly degenerate. We have further observed rich quasi-particle electronic structures of transition metal dichalcogenides as a function of atomic structures and spin-orbit couplings. Such a local probe for detailed electronic structures in conduction and valence bands will be ideal to investigate how electronic structures of transition metal dichalcogenides are influenced by variations of local environment.
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