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Ultranarrow resonance in Coulomb drag between quantum wires at coinciding densities

We investigate the influence of the chemical potential mismatch $Δ$ (different electron densities) on Coulomb drag between two parallel ballistic quantum wires. For pair collisions, the drag resistivity $ρ_{\rm D}(Δ)$ shows a peculiar anomaly at $Δ=0$ with $ρ_{\rm D}$ being finite at $Δ=0$ and vanishing at any nonzero $Δ$. The "bodyless" resonance in $ρ_{\rm D}(Δ)$ at zero $Δ$ is only broadened by processes of multi-particle scattering. We analyze Coulomb drag for finite $Δ$ in the presence of both two- and three-particle scattering within the kinetic equation framework, focusing on a Fokker-Planck picture of the interaction-induced diffusion in momentum space of the double-wire system. We describe the dependence of $ρ_{\rm D}$ on $Δ$ for both weak and strong intrawire equilibration due to three-particle scattering.