Using optical pumping we can create spin populations in semiconductors which turn into spin polarized current when an electric field is applied. If we use a ferromagnetic drain contact to suck up theses electrons we see that the drained current depends on the orientation of the electrons spin relative to the magnetization of the drain. Having a spin population which is not parallel to the magnetization simply makes it more likely for the electrons in the current to bounce off the interface of the semiconductor and drain.
The research being done by Dr. Furis (and S. A. Crooker, X. Lou, C. Adelmann, D. L. Smith, C. J. Palmstr∅m, P. A. Crowell) (please insert reference) brings together all of these ideas into the prototype (shown above) for a practical device (right now the devices are simply not practical because they require extreme cold [4 Kelvin] to function): a spin transistor.
Adjust the magnetic field and watch the electron precess before they decohere. Adjust the voltage and see how it effects the relaxation time and decoherence length.
A standard transistor is simply an electronic device
much like a mini switch. It has at least three
terminals. One terminal is called the source;
electrical current comes from this terminal and
travels to the drain contact, which sucks up the
current. The third terminal is called the gate
,
and controls the current running through the other two
by changing the number of free electrons
able
to conduct electricity, pulling them out of the
current. This makes the current larger or smaller,
turning the transistor on and off. Pulling the
electrons out of the current takes work, and energy.
Transistors are at the heart computer technology.
Computer chips are, for the most part millions of
little transistors linked together in logical
circuits.
A spin transistor is unique in the way the gate works. The gate is not controlled by an applied voltage on an electrical contact like it is in regular transistors. Instead of manipulating the number of electrons in the current to control the output, we are now attempting to use the spin population to controll the output at the drain. A magnetic field is the gate which controls the current in the device. Since the current through the transistor depends on the orientation of the spin population, and the orientation of the spin population can be controlled by a magnetic field (via spin precession) we can use the magnetic field to work as the gate, modulating the current between the source and drain. One great thing about the spin transistor is that to modulate the current, we expect less energy to be expended, in contrast to the classical transistor.
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