Electrical control of orbital and vibrational interlayer coupling in bi- and trilayer 2H-MoS$_2$

TL;DR

This study demonstrates electric field control over vibrational and electronic interlayer coupling in bi- and trilayer 2H-MoS$_2$, enabling tunable valley dichroism and phonon activation, with implications for opto-electronic device design.

Contribution

It introduces a method to manipulate interlayer coupling in MoS$_2$ using electric fields, revealing tunable valley polarization and phonon modes aligned with theoretical predictions.

Findings

Electric fields activate Raman phonon modes in MoS$_2$ layers.

Valley dichroism can be tuned up to 60% in bilayer and 35% in trilayer.

The delocalized electron wave function near Q points causes the tunable circular dichroism.

Abstract

Manipulating electronic interlayer coupling in layered van der Waals (vdW) materials is essential for designing opto-electronic devices. Here, we control vibrational and electronic interlayer coupling in bi- and trilayer 2H-MoS$_2$ using large external electric fields in a micro-capacitor 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 $\sim 60\%$ in bilayer and $\sim 35\%$ in trilayer MoS$_2$ that are 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.