Measurements of ballistic transport at nonuniform magnetic fields in cross junctions of a curved two-dimensional electron gas

摘要

We investigate ballistic transport in a high-mobility, two-dimensional electron gas, which is rolled up as a tube. The distinctiveness of our structure is that the electron's mean free path is as large as the radius of the tube. As a result free electron trajectories bend in space by about 60° while being confined in the curved quantum well. We observe negative bend resistances at zero magnetic field in cross junctions. In addition, the bend resistance becomes strongly asymmetric with respect to the orientation of the magnetic field due to varying magnetic field along the junction. The resistance asymmetry at low fields arises from trochoidlike trajectories, which carry electrons in the opposite direction as compared to the direction of conventional guided trajectories. At high magnetic fields, the interaction between closely separated channels of opposite velocity determines the bend resistance at the transition between integer filling factors.