Experimental studies of Coulomb drag between ballistic quantum wires

The Coulomb drag between two spatially separated one-dimensional (1D) electron systems in lithographically fabricated 2 µm long quantum wires is studied experimentally. The drag voltage VD shows peaks as a function of a gate voltage which shifts the position of the Fermi level relative to the 1D subbands. The maximum in VD and the drag resistance RD occurs when the 1D subbands of the wires are aligned and the Fermi wave vector is small. The drag resistance is found to decrease exponentially with interwire separation. In the temperature region 0.2 K⩽T⩽1 K, RD decreases with increasing temperature in a power-law fashion RD∝Tx with x ranging from -0.6 to -0.77 depending on the gate voltage. We interpret our data in terms of the Tomonaga-Luttinger liquid theory.