Coulomb drag: a probe of electron interactions in coupled quantum wells

As semiconductor devices shrink in size and in dimensionality, interactions between charge carriers become more and more important. There is a simple physical reason behind this behavior: fewer carriers lead to less effective screening, and hence stronger effective interactions. A point in case are one-dimensional systems (quantum wires): there electron-electron interactions may lead to a behavior, which is qualitatively different from the standard Fermi liquid picture (Luttinger liquids). Electron-electron interactions also play a central role in the fractional quantum Hall effect, which displays an extremely rich physical behavior, and remains a very active area for research. Thus there is a clear need for a better understanding of electron-electron interactions in dimensionally reduced semiconductor structures. We have reviewed recent developments in the theory of Coulomb drag. Our calculations lead to several predictions of effects not yet seen experimentally We conclude that Coulomb drag, in particular when combined with magnetic fields, is a very versatile tool for directly probing interparticle interactions in dimensionally restricted systems. A further line for research could be the study of quantum wires: there the interactions may lead to even more dramatic effects