Photoelectron Spin from Topological Insulators Controllable

Guest_Jim_* - March 26, 2013 12:29PM in Science & Technology

There are some weird materials out there, including topological insulators (TI) which will conduct light on their surface, but resist currents through their volume. Electrons flowing on a Tis surface do so in a specific alignment, with their spins oriented perpendicularly to their momentum. Researchers at Berkeley Lab and the University of California, Berkeley have recently discovered that once the electrons escape the TI surface, this orientation can be different, which has not been documented before.

One of the ways to study a topological insulator is to shoot a laser at it, causing an electron to be ejected from the material: the ejected electron is called a photoelectron. The properties of the photoelectron are then studied to learn about the TI, and typically the data takes a long time to collect. The researchers were working with a different set of equipment though that can increase the data collection rate, but some values were not quite right. Instead of using the powerful ALS, the researchers turned to a simpler laser which can have its polarization changed at will. As the researchers changed the laser's polarization they found that the spin polarization of the photoelectron also changed.

Typically researchers use the same polarization of light when studying Tis, so this effect had not been observed before. Now that it has been though, this optical control of the spin of an electron could find use in many advanced technologies, including spintronics.

Source: Berkeley Lab