Probing Critical Point Energies of Transition Metal Dichalcogenides: Surprising Indirect Gap of Single Layer WSe2

Nano Lett. 2015 Oct 14;15(10):6494-500. doi: 10.1021/acs.nanolett.5b01968. Epub 2015 Sep 25.


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.

Keywords: Transition metal dichalcogenides; critical points in Brillouin zones; interlayer coupling; scanning tunneling spectroscopy; spin−orbit coupling; variable Z spectroscopy.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chalcogens / chemistry*
  • Microscopy, Scanning Tunneling
  • Transition Elements / chemistry*


  • Chalcogens
  • Transition Elements