Nanospintronics brings about single-spin transistor

Physicists at the Institute for Microstructural Sciences (Ottawa) are the first to create a prototype of a single-spin transistor, which consists of a quantum dot connected to spin-polarised leads.

A quantum dot is an artificial atom in which electrons are confined spatially by an electrostatic potential much in the way that a nucleus localises electrons in an atom. The dot can be emptied and then electrons added one at a time to create a 'hydrogen' dot, 'helium' dot, 'iron' dot and so on.

By connecting the dot to spin-polarised reservoirs, one can insist that the electrons flowing in or out have their spins aligned up or down. This criterion can be used as a gate to allow a high or low current to flow through the dot.

In this way, the group was able to 'read' the spin properties of the dot. They could also 'write' by either adding an electron or by tuning the magnetic field. This unique combination of control at the single charge and single spin level may play a role in the future solid state form of quantum computing where the unit of quantum manipulation, the qubit, might consist of specially prepared spin states.