Electrical control of orbital and vibrational interlayer coupling in bi- and trilayer 2H-MoS2

Manipulating electronic interlayer coupling in layered van der Waals (vdW) materials is essential for designing optoelectronic devices. Here, we control vibrational and electronic interlayer coupling in bi- and trilayer 2H-MoS2 using large external electric fields in a microcapacitor device. The electric field lifts Raman selection rules and activates phonon modes in excellent agreement with ab initio calculations. Through polarization-resolved photoluminescence spectroscopy in the same device, we observe a strongly tunable valley dichroism with maximum circular polarization degree of similar to 60% in bilayer and similar to 35% in trilayer MoS2 that is fully consistent with a rate equation model which includes input from electronic band structure calculations. We identify the highly delocalized electron wave function between the layers close to the high-symmetry Q points as the origin of the tunable circular dichroism. Our results demonstrate the possibility of electric-field-tunable interlayer coupling for controlling emergent spin-valley physics and hybridization-driven effects in vdW materials and their heterostructures.