Far-infrared absorption of interaction-induced ground states of two weakly coupled quantum wires

We theoretically investigate the far-infrared (FIR) absorption of two weakly coupled vertical ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ quantum wires subjected to a perpendicular magnetic field. The calculations are performed within the time-dependent Hartree-Fock approximation. For a single occupied subband we find, depending on the electron density, different interaction-induced ground states. For small densities the interlayer exchange energy dominates, and we find a symmetric ground state with strong interlayer coherence. For larger densities the interplay of direct and exchange interaction drives the system into a state that shows the characteristics of a charge-density wave (CDW) in the direction of lateral confinement. The signatures of these states, the exchange enhanced tunneling gap of the coherent state and the density oscillations of the CDW, are directly reflected in the FIR spectrum.