It was recently predicted that it should be possible to use these constrictions to trap single spins, said Bird. In this paper, we provide evidence that such trapping can, indeed, be achieved with quantum point contacts and that it may also be manipulated electrically.
The system they developed steers the electrical current in a semiconductor by selectively applying voltage to metallic gates that are fabricated on its surface.
These gates have a nanoscale gap between them, Bird explained, and it is in this gap where the quantum point contact forms when voltage is applied to them.
By varying the voltage applied to the gates, the width of this constriction can be squeezed continuously, until it eventually closes completely, he said.
As we increase the charge on the gates, this begins to close that gap, explained Bird, allowing fewer and fewer electrons to pass through until eventually they all stop going through. As we squeeze off the channel, just before the gap closes completely, we can detect the trapping of the last electron in the channel and its spin.
The trapping of spin in that instant is detected as a change in the electrical current flowing through the other half of the device, he explained.
One region of the device is sensitive to what happens in the other region, he said.
Now that the UB researchers have trapped and detected single spin, the next step is to work on trapping and detecting two or more spins that can communicate with each other, a prerequisite for spintronics and quantum computing.
|Contact: Ellen Goldbaum|
University at Buffalo