Absence of Interlayer Tunnel Coupling of K -Valley Electrons in Bilayer MoS2

Abstract

In Bernal stacked bilayer graphene interlayer coupling significantly affects the electronic bandstructure compared to monolayer graphene. Here we present magnetotransport experiments on high-quality n-doped bilayer MoS2. By measuring the evolution of the Landau levels as a function of electron density and applied magnetic field we are able to investigate the occupation of conduction band states, the interlayer coupling in pristine bilayer MoS2, and how these effects are governed by electron-electron interactions. We find that the two layers of the bilayer MoS2 behave as two independent electronic systems where a two-fold Landau level's degeneracy is observed for each MoS2 layer. At the onset of the population of the bottom MoS2 layer we observe a large negative compressibility caused by the exchange interaction. These observations, enabled by the high electronic quality of our samples, demonstrate weak interlayer tunnel coupling but strong interlayer electrostatic coupling in pristine bilayer MoS2. The conclusions from the experiments may be relevant also to other transition metal dichalcogenide materials.Of the multitude of two-dimensional (2D) host materials, transition metal dichalcogenides (TMDs) are promising candidates for exploring quantum correlated electronic phases and electron-electron interaction effects due to their intrinsic 2D nature, large spin-orbit interaction and large effective mass carriers. Molybdenum disulfide (MoS 2

Excitons in a reconstructed moiré potential in twisted WSe2/WSe2 homobilayers

“…3C). While interlayer tunneling is strongly suppressed at the K-point in AB/BA-stacked bilayers (4,27), moving laterally to an oppositely stacked domain within the same layer is a faster process (28,29), especially for small domains (Fig. 3D).…”

Signature of Spin-Resolved Quantum Point Contact in p-Type Trilayer WSe2 van der Waals Heterostructure

“…9,10 To date, however, the number of electrostatically induced quantum confinement devices in TMDC or similar 2D materials 7,[11][12][13][14][15][16][17][18] was limited due to their poor crystal quality, mobility, ambient stability, and contact properties. Various methods such as doped or gated graphene contact, 7,17 phase engineering, 19,20 transferred top contact, 21,22 or bottom contact architecture [23][24][25] assembled in glove box was reliably realized for TMDC devices although the quality of low-temperature Ohmic contact is still limited. The Ohmic contact method for p-type material like WSe2 was realized via these methods whereas still high contact resistance and limited to inert atmosphere assembling.…”

Direct probing of phonon mode specific electron–phonon scatterings in two-dimensional semiconductor transition metal dichalcogenides

“…We find that the IETS spectra from the bilayer device, thus the electron–phonon scattering characteristics in WSe 2 bilayers, are distinct when compared with their monolayer counterparts, which we relate to the layer-number variant symmetry and the electronic structures around the conducting channels. Inversion symmetry preserved in bilayer 2H SC-TMDs renders interlayer tunneling at the K (K′) valley irrelevant because the interlayer couplings at the K (K′) points are weak around the conduction band edges 27 – 29 . Instead, strong interlayer hybridizations are prompted by the orbitals responsible for the conduction band edges at Q.…”

“…Therefore, in bilayer WSe 2 , electrons tunneled into the first layer from the graphite electrode with momentum K (K′) should be scattered off to Q (Q′) through intra- or intervalley electron–phonon scatterings (Fig. 1b ) before tunneling to the second layer 27 , 28 . Accordingly, single-phonon interlayer tunneling assisted by K phonons becomes limited in SC-TMD bilayers, leading to diminished inelastic tunnel features with the K phonons.…”