Metal to insulator quantum-phase transition in few-layered ReS₂

الأصل · EN

In ReS₂ a layer-independent direct band-gap of 1.5 eV implies a potential for its use in optoelectronic applications. ReS₂ crystallizes in the 1T′-structure which leads to anisotropic physical properties and whose concomitant electronic structure might host a non-trivial topology. Here, we report an overall evaluation of the anisotropic Raman response and the transport properties of few-layered ReS₂ field-effect transistors. We find that ReS₂ exfoliated on SiO₂ behaves as an n-type semiconductor with an intrinsic carrier mobility surpassing μᵢ 30 cm²/Vs at T = 300 K which increases up to 350 cm²/Vs at 2 K. Semiconducting behavior is observed at low electron densities n, but at high values of n the resistivity decreases by a factor > 7 upon cooling to 2 K and displays a metallic T²-dependence. This indicates that the band structure of 1T′-ReS₂ is quite susceptible to an electric field applied perpendicularly to the layers. The electric-field induced metallic state observed in transition metal dichalcogenides was recently claimed to result from a percolation type of transition. Instead, through a scaling analysis of the conductivity as a function of T and n, we find that the metallic state of ReS₂ results from a second-order metal to insulator transition driven by electronic correlations. This gate-induced metallic state offers an alternative to phase engineering for producing ohmic contacts and metallic interconnects in devices based on transition metal dichalcogenides.