Double-layer structures, consisting of two parallel quantum wells separated by a potential barrier,  are an important class of nanoscale electronic devices. Each layer hosts a quasi-two-dimensional electron  gas and electrons interact across the barrier via Coulomb interaction. The combined action of the spin and  pseudo-spin (associated with the layer index) degrees of freedom creates new phases in these bilayers  where the spin and many-body interaction effects play a critical role.  
	When an electric current is driven in one (active) layer of the bi-layer, the inter-layer Coulomb  interaction causes charge accumulation in the other (passive) layer. This phenomenon, known as Coulomb  drag, is of fundamental interest as a probe of electron correlations. Another effect of great interest is the  Spin Hall Effect, the generation of spin accumulation by an ordinary electric current. The spin Hall effect  is due to spin-orbit interaction and SOI and has been a subject of vigorous research both in  semiconductors and metals in recent years not only because of its theoretical subtlety but also as a  potential source of spin polarized currents.
	Lately, we have predicted and analyzed theoretically a new effect in bi-layers, which combines the  interesting features of spin Hall effect and Coulomb drag. We call it Spin Hall Drag. SHD consists in the  generation of spin accumulation across the passive layer by an electric current flowing along the other  layer. Besides being a striking example of an effect that depends simultaneously on Coulomb interactions  and spin-orbit coupling, the SHD has several unexpected and non-trivial features. It occurs in the absence  of a current in the passive layer and, as we have shown, it is predominantly caused by a subtle effect  known as side-jump in electron-electron collisions. This is at variance with the ordinary spin Hall effect,  which, for electrons in GaAs, is dominated by an effect known as skew-scattering. We have shown that  the skew-scattering and the side-jump contributions (considered for the first time in a context of electron-  electron scattering) are separated by different temperature dependences at low temperature T, with the  former vanishing much faster than the latter (T 3 vs T 2). Our calculations indicate that the induced spin  accumulation is large enough to be detected in optical rotation experiments.