Conductance anomalies in gated V-groove quantum wires

We present transconductance measurements on gated V-groove GaAs/AlGaAs quantum wire heterostructures grown by metal-organic chemical vapour deposition. The results show anomalously large negative magnetoresistance for a magnetic field perpendicular to the current, and oscillations in conductance with the field oriented along the width of the wire. Clear steps in conductance versus gate voltage are also observed and these are consistent with the charging of a nearby `droplet' with each step corresponding to a change in the occupation of a single electron.