High-Quality Electrostatically Defined Hall Bars in Monolayer Graphene.

Realizing graphene's promise as an atomically thin and tunable platform for fundamental studies and future applications in quantum transport requires the ability to electrostatically define the geometry of the structure and control the carrier concentration, without compromising the quality of the system. Here, we demonstrate the working principle of a new generation of high-quality gate-defined graphene samples, where the challenge of doing so in a gapless semiconductor is overcome by using the ν = 0 insulating state, which emerges at modest applied magnetic fields. In order to verify that the quality of our devices is not compromised, we compare the electronic transport response of different sample geometries, paying close attention to fragile quantum states, such as the fractional quantum Hall states that are highly susceptible to disorder. The ability to define local depletion regions without compromising device quality establishes a new approach toward structuring graphene-based quantum transport devices.