Figure 1

Figure 1: Schematic depiction of electron-hole packets in a two-dimensional electron gas (2DEG). (a) In the textbook description, the electron-hole packets drift in the direction of the applied field, with the holes leading the way. (b) In a high mobility 2DEG, the Coulomb drag correlation (indicated schematically by the wavy line) transfers momentum between electron and holes. The coupling creates an effective “drag field” on the holes, which reverses the drift so that the packets move in the direction opposite to the applied field. (The small separation between electron and hole density maxima is barely visible on the scale of this graph)