Experimental Evidence of Spin-Incoherent Luttinger Liquid State in Semiconductor Quantum wires*

We have measured the Coulomb drag between two spatially separated parallel quantum wires in the absence of tunneling to experimentally probe the recently proposed spin-incoherent Luttinger liquid (SILL) state. This new state is considered to exist in one-dimensional electron systems when the electron density is sufficiently low and the electron-electron interaction is strong, leading to \textit{J$<<$T$<<$E}$_{F}$, where $J $is the exchange coupling of spins and $E_{F}$ the Fermi energy. The measured drag resistance in the strictly one-dimensional (1D) transport regime is found to follow a power-law temperature dependence with a negative exponent (-0.65) in the temperature range 70mK -- 1.2K, in excellent agreement with the prediction of SILL theory for 4k$_{F}$ backscattering. The drag resistance is also found to decay exponentially with wire separation confirming the backscattering nature of the momentum transfer process.