Experimental observation of Coulomb drag in parallel ballistic quantum wires

We report the experimental observation of Coulomb drag in two parallel, ballistic quantum wires fabricated from a high-mobility 2DEG at the interface of a AlGaAs/GaAs heterostructure and defined by three independent Schottky gates. The Coulomb drag resistance R-D in wire 1 due to a drive current in wire 2 was measured at 1.3 It and in a magnetic field of 1 T, applied to completely suppress tunneling between the wires when their separation was small. As the widths of the wires are changed by appropriately biasing the Schottky gates, R-D shows a structure with peaks whose magnitudes decrease rapidly with the distance d between the centers of the wires, These results can be understood qualitatively in the framework of recent theoretical treatments, which predict peaks in R-D when the level splitting between the 1D subbands of the wires and the Fermi momentum k(F) are small. The peak is strongest for the lowest subbands and weakens;ens rapidly for higher ones. (C) 2000 Published by Elsevier Science B.V. All rights reserved.