Collective excitations in spontaneously spin-polarized phases of semiconductor double-quantum-well systems

The intersubband collective modes of the spontaneously spin-polarized phases of semiconductor double-quantum-well systems have been analyzed, generalizing the time-dependent local-spin-density approximation for a consistent treatment of exchange-correlation effects in spin-polarized phases. Abrupt changes in the charge- and spin-density-related collective modes are found as the system passes from unpolarized to polarized ground states through first-order transitions. Excellent agreement with available experimental data is found if the tunneling-induced gap is considered as an adjustable parameter. A suggestion is made that for a tunneling-induced gap of about 0.35 meV the polarized phases should be observable at experimentally accessible densities.