Regime of a single 1D wire subband filled. Credit: Dr Maria Moreno
Researchers have observed quantum effects in electrons by squeezing them into one-dimensional ‘quantum wires’ and observing the interactions between them. The results could be used to aid in the development of quantum technologies, including quantum computing. Squeezing electrons into a one-dimensional ‘quantum wire’ amplifies their quantum nature to the point that it can be seen, by measuring at what energy and wavelength (or momentum) electrons can be injected into the wire.
“…for electrons in a quantum wire – they repel each other and cannot get past, so if one electron enters or leaves, it excites a compressive wave like the people in the train,” trying to leave a carriage, said Maria Moreno, also from the Cavendish Laboratory. However, electrons have another characteristic, their angular momentum or ‘spin’, which also interacts with their neighbours. Spin can also set off a wave carrying energy along the wire, and this spin wave travels at a different speed to the charge wave. Measuring the wavelength of these waves as the energy is varied is called tunnelling spectroscopy. The separate spin and charge waves were detected experimentally by researchers from Harvard and Cambridge Universities.
Now Cambridge researchers have gone one stage further, to test the latest predictions of what should happen at high energies, where the original theory breaks down. A flurry of theoretical activity in the past decade has led to new predictions of other ways of exciting waves among the electrons. These new ‘modes’ are weaker than the spin and charge waves and so are harder to detect.
The collaborators predicted that there would be a hierarchy of modes corresponding to the variety of ways in which the interactions can affect the quantum-mechanical particles, and the weaker modes should be strongest in very short wires. To make a set of such short wires, the Cambridge group set about devising a way of making contact to a set of 6000 narrow strips of metal that are used to create the quantum wires from the semiconducting gallium arsenide (GaAs). This required an extra layer of metal in the shape of bridges between the strips.
By varying the magnetic field and voltage, the tunnelling from the wires to an adjacent sheet of electrons could be mapped out, and this revealed evidence for the extra curves predicted, where it can be seen as an upside-down replica of the spin curve. These results will now be applied to better understand and control the behaviour of electrons in the building blocks of a quantum computer.
http://infowebbie.com/scienceupdate/modern-alchemy-researchers-reveal-magnetic-rust-performs-gold-nanoscale/ http://www.cam.ac.uk/research/news/a-tight-squeeze-for-electrons-quantum-effects-observed-in-one-dimensional-wires
Recent Comments