ABSTRACT
Here, we solve both issues related to the classical “fundamental obstacle” [6-9] and the material-dependent limitations by using a mechanism for spin-injection and detection that di¥ers fundamentally from ohmic transport in that (1) the inelastic mean free path (mfp) is not the smallest length scale in the device and that (2) electrochemical potentials cannot be uniquely de¢ned in thermal equilibrium. With these techniques, the physical length scale of the metallic electron injection contacts is shorter than the mfp, and conduction occurs through states far above the Fermi level (as compared to the thermal energy kBT), far out of thermal equilibrium. Because this transport mode utilizes electrons with high kinetic energy that do not su¥er appreciable
inelastic scattering, it is known as “ballistic hot-electron transport.” Both spin injection and detection are performed all-electronically, and interfacial structure [10] plays only a minor role, enabling observation and study of spin transport in materials such as Si, which had been previously excluded from the ¢eld.
