Current-driven plasma instabilities in parallel quantum-wire systems

A theory of current-driven plasma instability in a double-quantum-wire system is presented. It is shown that, if the wires carry steady currents in opposite directions, the quasi-one-dimensional (quasi-1D) plasma waves propagating along the wires become unstable when the electron drift velocity falls between the phase velocities of the acoustic and optical plasma modes of the Coulomb-coupled quantum wires. Such an instability occurs at experimentally achievable drift velocities because of the softening of the plasma waves in 1D wires. The condition for plasma instability in a lateral double-quantum-wire superlattice is also determined.