Ultrafast near-field spectroscopy of quasi-one-dimensional transport in a single quantum wire

Quasi-one-dimensional carrier transport is studied in a single ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/\mathrm{GaAs}$ quantum wire by combining two-color femtosecond pump and probe spectroscopy and near-field optical microscopy. Evidence is found for a transient nonambipolar electron transport along the wire axis on a picosecond time and 100 nanometer length scale.