Coulomb drag between two spin-incoherent Luttinger liquids

In a one-dimensional electron gas at low enough density, the magnetic (spin) exchange energy J between neighboring electrons is exponentially suppressed relative to the characteristic charge energy, the Fermi energy EF. At nonzero temperature T, the energy hierarchy J T EF can be reached, and we refer to this as the spin-incoherent Luttinger liquid state. We discuss the Coulomb drag between two parallel quantum wires in the spin-incoherent regime, as well as the crossover to this state from the low-temperature regime by using a model of a fluctuating Wigner solid. As the temperature increases from zero to above J for a fixed electron density, the 2 kF oscillations in the density-density correlations are lost. As a result, the temperature dependence of the Coulomb drag is dramatically altered and nonmonotonic dependence may result. Drag between wires of equal and unequal density are discussed, as well as the effects of weak disorder in the wires. We speculate that weak disorder may play an important role in extracting information about quantum wires in real drag experiments.