SINGLE MAGNETIC-FLUX TUBE IN A MESOSCOPIC 2-DIMENSIONAL ELECTRON-GAS CONDUCTOR

An influence of a single magnetic flux tube, having submicron dimensions and carrying a flux quantum h/2e, on the electron transport in a micron-sized conductor has been studied. Small magnetic tubes were produced by sputtering a type-II superconducting film onto the surface of GaAs/GaAlAs heterostructure. A random magnetoresistance caused by the entrance of a vortex into the two-dimensional electron gas (2DEG) was observed, indicating a complete change of the quantum interference pattern in the sample. The weak localization part of the vortex induced magnetoresistance appeared to be much smaller than its random (mesoscopic) part and also substantially smaller than a value predicted by theory. This behaviour is attributed to a breakdown of the diffusion approximation. The Hall effect was found to be insensitive to the distribution of the magnetic field.