Metal-insulator transitions in bilayer electron-hole systems in transition metal dicalcogenides

TL;DR

This paper studies the conditions under which bilayer electron-hole systems in transition metal dichalcogenides undergo metal-insulator transitions, highlighting the role of interactions and screening in these 2D materials.

Contribution

It introduces a detailed computational approach to predict metal-insulator transitions in TMDC bilayers considering screening effects and valley degeneracy.

Findings

Transition densities are within experimentally accessible ranges.

Screening effects significantly influence the transition.

Potential for logic device applications is identified.

Abstract

We investigated metal-insulator transitions for double layer two-dimensional electron hole systems in transition metal dicalcogenides (TMDC) stacked on opposite sides of thin layers of boron nitride (BN). The interparticle interaction is calculated by including the screening due to the polarization charges at different interfaces, including that at the encapsultion and the substrate of experimental structures. We compute and compare the energies of the metallic electron-hole plasma and the newly proposed insulating exciton solid with fixed-node diffusion Monte Carlo simulation including the high valley degeneracy of the electron bands. We found that for some examples of current experimental structures, the transition electron/hole density is in an accessible range of g x 10^12 /cm*2 with g between 4.1 and 14.5 for spacer thicknesses between 2.5 and 7.5 nm. Our result raise the possibility of exploiting this effect for logic device applications.