Effetcs of thickness and mass anisotropy on the spin susceptibility of the 2DEG in AlAs QWs

It has been demonstrated that device details, such as the transverse thickness, may affect in a substanial manner the spin susceptibility of the two dimensional electron gas (2DEG) which is realized in semiconducting heterostructures [1]. An important device detail in AlAs quantum wells(QW) is an in-plane mass anisotropy [2], which even in the regime with only one valley occupied is combined with a sizeable transverse thickness. For selected values of the well width appropriate to the experiments, we evaluate the effect of such thickness and, partly, of the mass anisotropy through a mapping of the 2DEG with mass anisotropy onto an `equivalent' isotropic 2DEG with effective mass $m^*=\sqrt{m_tm_l}$. We then critically compare our results with experimental meausurent and assess the importance of anisotropy effects that go beyond this simple minded mapping. \newline [1] S. De Palo et. al., Phys. Rev. Lett. 94, 226405 (2005). \newline [2] M. Shayegan et. al., phys. stat. sol. (b) 243, 3629 (2006)