Advances in semiconductor heterostructure growth and lithography have made it possible now to build gate-defined nanostructures small enough to confine a single electron. Gates provide an extraordinary degree of control over the interactions in these systems, in effect implementing arbitrary hamiltonians on a chip. Due to the weak interaction between electronic or nuclear spins and any measurement apparatus, we use charge transport is as a more sensitive probe of spin physics in mesoscopic structures. Recently we measured conductance fluctuations to examine the spin-orbit interaction in confined GaAs structures, and Coulomb blockade peak motion in a magnetic field to probe quantum dot spin states. We then developed a focusing geometry that used charge currents to detect spin currents from quantum point contacts and quantum dots.
Semiconductor nanostructures have proven to be an exceedingly powerful and flexible platform to study effects ranging from the interaction of a single electron spin with a continuous Fermi sea (the Kondo effect) to the interaction between two confined electrons (coupled quantum dots). The next few years will bring experiments that involve complex interactions between multiple electrons. These experiments will take advantage of the spin-orbit and hyperfine interactions of the host semiconductor systems, and will require control over single electron spins as well as many-particle entangled states.
