COLLECTIVE EXCITATIONS IN REALISTIC QUANTUM WIRES

We have used the Hartree-Fock random phase approximation to study the interacting electron gas in a quantum wire. The spectra of intersubban d spin-hip excitations reveal a considerable red shift with respect to single-particle Hartree-Fock energies. That signals the appearance of collective intersubband spin-density excitations due to the exchange interaction. The long-wavelength dispersions of the intrasubband colle ctive spin-density excitations are linear but the sound velocities are renormalized due to the exchange interaction and screening. The in-ph ase intrasubband charge-density excitation has the long-wavelength for m g[-ln(q)](1/2). We found good qualitative agreement of our results w ith experimental observations.