Collective and transport properties of the two-dimensional electron gas with spin-orbit coupling
Final Report Abstract
In the present project we have investigated the full frequency and momentum dependence of the density response matrix function of the two-dimensional electron gas with spin-orbit (SO) coupling. Its components describe a response of the system to external charge and spin density perturbations (local electric and magnetic fields). Due to the momentum dependence of the spin-orbit coupling there emerge new specific features in the system's properties. We have established how the transitions between SO-split subbands affect the polarizability of the system and the properties of the collective charge density oscillations. We have also observed that in the similar way the SO coupling can affect the lifetime of the longitudinal optical phonon. We have investigated the spin-density response to the external charges as well as the reciprocal effect. Both of them become possible in the presence of the SO coupling. The existence of nonvanishing spin-charge off-diagonal term in the matrix response function leads to a formation of nontrivial mixtures of the collective charge and spin density modes. The latter can be visible in the spectral properties of the renormalized susceptibilities. In particular, due to the spin-charge mixing it becomes possible to observe by means of inelastic Raman scattering the sharp plasmon-like peak in the in-plane magnetization, which has no analogies in the absence of spin-orbit coupling. This is a result of the nontrivial interplay of the SO coupling and the exchange interaction. We have established the correct expressions for the charge and spin susceptibilies in the static limit. On their basis we have considered the modifications of the Kohn anomaly and spatial behavior of the effective potential as well as of the RKKY interaction due to the SO coupling. We have also studied the role of impurities and described the crossover from the diffusive to the ballistic regimes in the system's response in the presence of the SO coupling. We have observed a possibility for propagating density modes with spin-resolved dispersions for the case of the SO splitting larger than a disorder broadening. The calculated response functions can serve as a basis for subsequent studies of correlation effects in the two-dimensional electron gas with the SO coupling. The SO-induced damping of the collective modes (plasmons, magnons, phonons) as well as the SO-induced features in the lineshapes of the charge and spin susceptiblities can be verified experimentally.
Publications
- M. Pletyukhov and S. Konschuh, Charge and spin density response functions of the clean two-dimensional electron gas with Rashba spin-orbit coupling at finite momenta arid frequencies, Eur. Phys. J. B 60, 29 (2007).
- M. Pletyukhov and V. Gritsev, Screening in the two-dimensional electron gas with spin-orbit coupling, Phys. Rev. B 74, 045307 (2006).
- M. Pletyukhov, Crossover from diffusive to nondiffusive dynamics in the twodimensional electron gas with Rashba spin-orbit coupling, Phys. Rev. B 75, 155335 (2007).
