High tunability of the transport properties in macroscopically in-plane modulated two-dimensional system
Gate-controllable two dimensional systems with in-plane modulation of properties could serve as highly tunable effective media. Intuitively, such systems may bring novel functionality provided that the period of the lateral modulation is much less than the relevant scattering lengths (mean free path, coherence length etc.). Our work experimentally demonstrates the opposite, disordered limit of such system, defined in the macroscopically modulated metal-oxide-semiconductor structure. The system consists of parent two-dimensional gas with periodic array of islands (dots/antidots), filled with two-dimensional gas of different density, and surrounded by depletion regions (shells). Carrier densities of both parent gas and islands are controlled by two independent gate electrodes, allowing us to explore a rich phase diagram of low-temperature transport properties of this modulated two-dimensional system, resembling various transport regimes: insulating, shell-dominated, gas-dominated, island-dominated. These regimes can be identified by various Hall resistance and its magnetic field dependence, temperature dependencies of the resistivity, and Shubnikov-de Haas patterns. We also suggest the theoretical approach for description of such inhomogeneous but periodical systems. Theory based on the classical mean field approach qualitatively describes our system as theoretical dependencies reproduce the main features of the experimental behavior of the effective Hall concentration from gate voltage. Thus, our work demonstrates feasibility of the macroscopically inhomogeneous two-dimensional system as a tunable platform for novel physics and proposes the approach for the theoretical description of such systems.