Recently researchers in Russia have constructed specially built vacuum tubes that allow the properties of electron spin to be studied. The tubes, shown below, allowed the researchers to determine important characteristics of spin-polarized electrons, such as their ‘spin’ diffusion length. In addition, they were able to construct a prototype spin filter/detector which may potentially even have commercial applications.
The spin of an electron can be thought of as a quantum property that can have either one of two values. This, from an engineering point of view, could be exploited in the new field of ‘Spintronics’ (Spin Transport Electronics). In which, unlike traditional electronics, the spin state rather than the flow of electrons can represent information. This potentially could result in novel devices such as the spin transistor, which could potentially have lower power consumption and directly lead to computers which have grater storage capacities.
However, plenty of obstacles must be overcome before such devices can be implemented. Most of these obstacles are related to our limited understanding of spin polarized electrons and their interaction with solid-state structures. This is where specially built and modified tubes could continue to play a crucial role. The researchers were able to conduct experiments that allowed them to gain invaluable results that could help explain spin dependent phenomenon. Vacuum tubes are ideal for such studies as they naturally allow charged particles to flow unimpeded and hence allow us to determine their associated energies. Additionally, unlike open setups, the devices are less prone to contamination and as a result have longer life-times. This allows results to be reproducible as the equipment has a reliably long lifetime.
Custom built vacuum tubes.
Setup (a) measures spin dependent photoemission.
Setup (b) measures spin dependent reflection. 1) Photocathode unit, 2) anode, 3) metal-ceramic body, 4) non-evaporated getter, 5) copper micromesh, 6) Venetian blind dynode (emits secondary electrons). Both tubes are only a few centimetres in length and diameter.
Further Reading/ References:
1. V.L. Alpervich and co. (Aug 2009), “Compact Vacuum Tubes with GaAs photocathodes for studying spin-dependent phenomena”, Proc. Of SPIE Vol. 7398 739818
2. Awschalom, David & co., Semiconductor spintronics and quantum computation, (USA, 2002)
3. Greene, Kate. A bright future for spintronics, Technology Review: http://www.technologyreview.com/computing/17622/page1/