Coulomb Drag in 2D bilayer Topological Insulator systems*

InAs/GaSb quantum wells are 2D bilayer topological insulator systems possessing the inverted band structure with the conduction band bottom of the InAs layer below the valence band top of GaSb layer. Recent transport experiment in InAs/GaSb quantum wells has revealed an anomalous high frequency quantum oscillation coexisting with a large resistance when the chemical potential is tuned into the charge neutrality point. The high oscillation frequency (large carrier density) and large resistance (insulating behaviors) are in contradiction with each other and this fact cannot be explained in a single-particle picture, thus motivating us to study the interaction effect of this system. Based on the linear response theory and diagrammatic methods, we carefully investigated the Coulomb drag effect in this 2D topological insulator systems based on the simplified models. Our results shed the light in understanding the anomalous quantum oscillation in 2D bilayer topological insulator systems.