Direct Measurement of the Tunable Electronic Structure of Bilayer MoS2 by Interlayer Twist

Nano Lett. 2016 Feb 10;16(2):953-9. doi: 10.1021/acs.nanolett.5b03883. Epub 2016 Jan 20.


Using angle-resolved photoemission on micrometer-scale sample areas, we directly measure the interlayer twist angle-dependent electronic band structure of bilayer molybdenum-disulfide (MoS2). Our measurements, performed on arbitrarily stacked bilayer MoS2 flakes prepared by chemical vapor deposition, provide direct evidence for a downshift of the quasiparticle energy of the valence band at the Brillouin zone center (Γ̅ point) with the interlayer twist angle, up to a maximum of 120 meV at a twist angle of ∼40°. Our direct measurements of the valence band structure enable the extraction of the hole effective mass as a function of the interlayer twist angle. While our results at Γ̅ agree with recently published photoluminescence data, our measurements of the quasiparticle spectrum over the full 2D Brillouin zone reveal a richer and more complicated change in the electronic structure than previously theoretically predicted. The electronic structure measurements reported here, including the evolution of the effective mass with twist-angle, provide new insight into the physics of twisted transition-metal dichalcogenide bilayers and serve as a guide for the practical design of MoS2 optoelectronic and spin-/valley-tronic devices.

Keywords: MoS2; Stacked van der Waals structures; low energy electron microscopy (LEEM); photoemission; spectromicroscopy; twisted van der Waals materials.

Publication types

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