PHYSICS WORLD - Taking inspiration from the flow of air around aeroplane wings, researchers in the US have imaged photoexcited electrons flowing around sharp bends for the first time. Because such bends are often found in integrated optoelectronic circuits, observing the electrons’ “streamlines” could lead to improvements in circuit design.
More than 80 years ago, the physicists William Shockley and Simon Ramo showed theoretically that when electrons travel around bends, their streamlines get locally compressed, producing heat. Until now, though, no-one had measured this effect directly because it is so difficult to observe the streamlines of electron photocurrents – that is, electric currents induced by light – through a working device.
In the new work, which is described in the Proceedings of the National Academy of Sciences, researchers led by physicists Nathaniel Gabor and David Mayes of the University of California, Riverside built a micromagnetic heterostructure device made from a layer of platinum on a yttrium iron garnet (YIG) substrate and placed it in a rotating magnetic field. They then directed a laser beam onto the YIG, causing the device to heat up and triggering a phenomenon known as the photo-Nernst effect. It is this effect that generates the photocurrent.