Quasi-1D Coulomb drag between spin-polarized quantum wires

One-dimensional (1D) quantum wires provide a versatile platform for studying strong electron-electron interactions and collective excitations under confinement. Coulomb drag between 1D systems offers a powerful probe of Tomonaga-Luttinger liquid (TLL) physics, with theoretical predictions suggesting distinct power-law in temperature dependencies between the spin-full and the spin-polarized regimes. However, experimental verification has thus far remained limited. Here, we report measurements of reciprocal and nonreciprocal Coulomb drag between vertically coupled quasi-1D disordered quantum wires in the spin-polarized regime. Clear signatures of spin splitting are observed in both the wires' conductance and in the drag signal. The 1D Coulomb drag signal exhibits different power-law behaviors in the spin-full and spin-polarized regimes, yielding consistent TLL interaction parameters. These results are in qualitative agreement with theoretical predictions for backscattering-induced drag in the reciprocal regime of single-subband ballistic quantum wires, and show these predictions remain valid in the disordered, nonreciprocal, and multiple-subband regimes.