We investigate a two-dimensional electron model with Rashba spin-orbit interaction where the coupling constant g=g(n) depends on the electronic density. It is shown that this dependence may drive the system unstable towards a long-wave length charge density wave (CDW) where the associated second order instability occurs in close vicinity to global phase separation. For very low electron densities the CDW instability is nesting-induced and the modulation follows the Fermi momentum kF. At higher density the instability criterion becomes independent of kF and the system may become unstable in a broad momentum range. Finally, upon filling the upper spin-orbit split band, finite momentum instabilities disappear in favor of phase separation alone. We discuss our results with regard to the inhomogeneous phases observed at the LaAlO3/SrTiO3 or LaTiO3/SrTiO3 interfaces.
@article{arxiv.1407.4280,
title = {Phase separation and long wave-length charge instabilities in spin-orbit coupled systems},
author = {G. Seibold and D. Bucheli and S. Caprara and M. Grilli},
journal= {arXiv preprint arXiv:1407.4280},
year = {2015}
}