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

We investigated metal-insulator transitions for double-layer two-dimensional electron-hole systems in transition metal dichalcogenides stacked on opposite sides of thin layers of boron nitride. The interparticle interaction is calculated by including the screening due to the polarization charges at different interfaces, including that at the encapsulation and at the substrate of experimental structures. We compute and compare the energies of the metallic electron-hole plasma and the 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 experimentally accessible range between $4.1\ifmmode\times\else\texttimes\fi{}{10}¹²\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$ and $14.5\ifmmode\times\else\texttimes\fi{}{10}¹²\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$ for spacer thicknesses between 2.5 and 7.5 nm. Our result raises the possibility of exploiting this effect for logic device applications.