In 1971, Mikhail Dyakonov and Vladimir Perel of the Ioffe Institute in Leningrad proposed a new transport phenomenon. 1 If one applies an electric field to the ends of a semiconducting strip, they reasoned, electrons would scatter off impurities in a spin-dependent way. As the electrons make their way along the strip, those with up spins would veer to one side, while those with down spins would veer to the other side.
The result is a transverse flow of spin, a “spin Hall effect.” Unlike the traditional Hall effect and its younger quantum cousins, the spin Hall effect doesn’t cause a transverse voltage. Nor does it need an external magnetic field. The polarization relies instead on the relativistic coupling of the electron’s spin and orbital angular momentum.
But the predicted polarization is modest. For two decades after its debut, Dyakonov and Perel’s proposal languished as a curiosity, all but ignored...
