Drag measurements of two-dimensional semiconductor double layers

Interlayer dipolar excitons in semiconductor double layers provide a promising platform for studying Bose-Einstein condensation with tunable coupling strength at zero magnetic field. Progress has been made in realizing exciton condensates in double layer transition metal dichalcogenides, but transport measurement remains a problem due to the difficulty of making independent Ohmic contacts to each layer. Here we address this challenge using a new fabrication technique based on assembling pre-patterned, contamination-free two-dimensional flakes. I demonstrate drag and counterflow transport measurements of WSe2 double-layer devices. The work paves the way for innovative device architectures with built-in nanostructures.