GAPLESS SPIN EXCITONS IN PERIODICALLY MODULATED 2-DIMENSIONAL ELECTRON-GAS

The spin-exciton band structure in a periodically modulated two-dimensional electron gas, under strong magnetic fields, is shown to be unusually rich due to the peculiar nature of the free exciton dispersion law. It is found that the periodic modulation potential can distort the single spin excitonic state so strongly that the energy gap in the spectrum disappears. It is argued that these gapless spin excitons radically affect the nuclear spin transport in the heterojunction via the hyperfine interaction and may condense into a collective spin density wave ground state. © 1994 The American Physical Society.