Starts 9 Sep 2009 17:00
Ends 9 Sep 2009 20:00
Central European Time
Leonardo da Vinci Building Seminar Room
Strada Costiera, 11 I - 34151 Trieste (Italy)
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.